|
|
Bulletin Volume
11, Issue 2, Fall / Winter 2005
Articles in this issue:
Brain
Injury and Pituitary Dysfunction
Lisa B. Nachtigall, M.D.
It has been
known for over 80 years that brain injury may be associated
with hypopituitarism, but recent evidence shows an even higher
prevalence of anterior pituitary deficiencies than previously
thought. A summary of the recent data on the prevalence of anterior
pituitary deficiencies in sub-arachnoid hemmorage (SAH) and
traumatic brain injury (TBI) survivors including the incidence
of specific hormonal deficiencies reported is shown in Table
1.
Prevalence
of Posttraumatic Posterior Pituitary Hormone Deficiencies
|
"There
is increasing evidence that pituitary hormone deficiencies
occur following traumatic brain injury or subarachnoid
hemorrhage."
|
Disorders
of water balance are well recognized after TBI, but there are
limited reliable data on their true prevalence in post- TBI
patients. In one study of 102 patients, 21.6% developed diabetes
insipidus (DI) in the immediate post-TBI period and permanent
DI remained in 7% of patients (1). In the acute post-TBI period,
13 patients (12.9%) had syndrome of inappropriate secretion
of antidiuretic hormone, which persisted in one patient, and
one other patient developed cerebral salt wasting (1). Identification
of patients with water imbalance is important because appropriate
treatment may reduce morbidity and optimize the potential for
recovery.
Prevalence
of Posttraumatic Anterior Pituitary Hormone Deficiencies
In short-term
studies, approximately 35% of patients have at least one deficiency
within three months of the initial injury (2-4). Long-term survivors
of both TBI and aneurysmal SAH have been found to have a 3055%
prevalence of at least one anterior pituitary deficiency when
evaluated up to six years after the initial injury (5-8). The
prevalence of anterior pituitary dysfunction was even higher
in one study of TBI survivors when neuroendocrine testing was
performed more acutely (7 to 20 days after the trauma) in which
80% of subjects had gonadotropin deficiency (4). However, in
this study hyperprolactinemia was present in half the subjects,
which could have been the result of medications or seizures
complicating the acute phase of injury. Thus, hyperprolactinemia
may have caused the high rate of gonadotropin deficiency unique
to this study of hormonal changes within three weeks of injury.
The type
of brain injury may relate to the frequency and type of pituitary
hormone deficiencies. Given that corticotropes are thought to
be more resistant to injury than gonadotrophs and somahere totrophs,
it is surprising that a long-term study in SAH patients shows
a higher incidence of central adrenal insufficiency (40%) and
a lower incidence of central hypogonadism than in studies comprised
predominantly of TBI patients (6). Potential confounding variables
include age and gender. The SAH group contains mostly women
who were older, while the TBI subjects were mostly male and
significantly younger on average. In addition, different methods
of dynamic testing were used. Finally, the long-term SAH did
not specifically cite exogenous glucocorticoid use as exclusion
criterion, although authors mention that a history of steroid
use was not documented in the majority of cases Interestingly,
a short-term study which evaluated a similar group of older
women at three monthsafter the initial hemorrhage, had opposite
findings, with a very low prevalence of adrenal insufficiency
(3%) (3). This suggests that it may be important to evaluate
patients beyond the initial three months, as hypoadrenalism
may not become apparent until later. More consistent findings
were reported in several recent studies regarding growth hormone
deficiency and central hypothyroidism, which occurred in approximately
25% and 5% of brain injured subjects respectively (2-8).
Risk
Factors for Hypopituitarism in Patients with Brain Injury
The risk
factors for developing hypopituitarism after cerebral injury
have not been determined. Several short-term studies suggest
that severity of injury correlates with a higher rate of loss
of anterior pituitary function within three months of the event
(2,4). With a single exception (5), the long-term studies showed
no correlation between loss of pituitary function and severity
of brain injury, edema or anatomic findings on brain imaging
(6-8). The discrepancy among results raises the question as
to when testing of hormone deficiencies should be conducted.
Since longitudinal observations from prospective studies have
not yet been reported, the timing of onset and the duration
of specific anterior pituitary deficiencies have not been determined.
In a review by Benvenga, it was clear that in the majority of
TBI cases, pituitary deficiencies were discovered within the
first year after the trauma (9). However, in about 5% of patients
with posttraumatic hypopituitarism, there was an over 20-year
lag period between injury and diagnosis (9). Individual studies
vary in the number and selection criteria of subjects and the
methods of dynamic pituitary testing, possibly accounting for
the differences in specific patterns of pituitary deficiencies
reported. Prospective studies will be necessary to establish
the timing of hormone loss after brain injury.
Pathophysiology
of Hypopituitarism after Brain injury
The pathophysiology
of pituitary deficiencies following brain injury has not yet
been elucidated. Hypoxic or hypotensive crises and/or raised
intracranial pressure causing hypothalamic damage could be postulated,
but these hypotheses have not been systematically studied and
it is unknown whether the deficiencies identified are hypothalamic
or pituitary in origin. In autopsy studies of patients who died
due to TBI, there is an up to 50% incidence of hemorrhage in
the pituitary capsule and up to 30% incidence of either necrosis
of the anterior pituitary or stalk hemorrhage (9). However,
the autopsy studies include the most severe cases, those who
died from the acute trauma, and may not reflect the pathophysiology
of long-term pituitary failure in survivors.
|
Table
I. Hypopituitarism After Brain
Injury: Summary of Recent Reports Author/year
|
Number
of Subjects (male/female)
|
Age
of subjects (mean years)
|
TBI
or SAH
|
Time
since injury (mean months)
|
%
At least 1 pituitary hormone deficiency
|
AI
%
|
GHD
%
|
HH
%
|
CH %
|
|
*Kelly
2000 (2)
|
26
(18/6)
|
28
|
both
|
3
|
37
|
4
|
29
|
17
|
4
|
|
Aimaretti
2004 (3)
|
100 (69/31)
|
37
|
TBI
|
3
|
35
|
8
|
25
|
4
|
5
|
|
Aimaretti
2004 (3)
|
40
(14/26)
|
51
|
SAH
|
3
|
38
|
3
|
25
|
13
|
8
|
|
*Agha
2004 (4)
|
50
(38/12)
|
37
|
TBI
|
0.5
|
80
|
16
|
18
|
80†
|
2
|
|
Lieberman
2001(8)
|
70
(46/24)
|
32
|
both
|
49
|
54
|
7
|
15
|
3
|
11
|
|
Agha
2004 (7)
|
102 (85/17)
|
28
|
TBI
|
17
|
28
|
23
|
18
|
12
|
7
|
|
Kreitschmann-
(6) Andermahr 2004
|
40
(14/26)
|
44
|
SAH
|
27
|
55
|
40
|
20
|
0
|
3
|
|
*Bondanelli
2004 (5)
|
50
(40/10)
|
38
|
TBI
|
12
– 64 (range)
|
54
|
0
|
28
|
14
|
10
|
|
AI
= adrenal insufficiency GHD = growth hormone deficiency
HH = hypogonadotropic hypogonadism CH = central hypothyroidism
*indicates significant correlation between severity of
injury and prevalence of pituitary hormone deficiency
SAH = subarachnoid hemorrhage, TBI = traumatic brain injury
both = subjects with SAH and TBI were included
† = this includes 50% of patients that had hyperprolactinemia as possible cause
of HH
|
While the
etiology of the pituitary dysfunction is unknown, these hormonal
deficiencies may have significant impact on quality of life.
Fatigue, cognitive dysfunction and depression are known to limit
rehabilitative progress and quality of life in these patients.
Such symptoms could potentially stem from or be compounded by
a treatable, unrecognized pituitary hormone deficiency (10-12).
Furthermore, cardiovascular disease has been found to be the
most important cause of death in longterm SAH survivors
and an excessive mortality from cardiovascular disease has been
reported in patients with hypopituitarism (13). Thus, hypopituitarism
is a potential factor contributing to the excess cardiovascular
mortality in brain injury survivors. Unrecognized adrenal insufficiency
is also a potential cause of morbidity and of mortality if adrenal
crisis occurs.
Neuroendocrine
Testing
Given the
published data currently available, it is reasonable to suggest
routine neuroendocrine testing for survivors of brain injury.
Which tests to perform and when to perform them in a cost effective
and practical manner has not been formally examined. Using general
principles of neuroendocrine testing for hypopituitarism, initial
evaluation might include assessment of serum free T4, TSH, AM
cortisol, prolactin, IGF-1, testosterone (in men) and FSH (in
postmenopausal and/or premenopausal women with amenorrhea).
If the AM cortisol is less than 3 ug/dl, the diagnosis of adrenal
insufficiency is established. If the AM cortisol is greater
than 18 ug/dl, then adrenal insufficiency is excluded in most
patients. Levels of serum AM cortisol between 3 ug/dl and 18
ug/dl warrant a cortrosyn stimulation test, which should be
done at least 6-12 weeks after the initial injury, as earlier
testing may yield false negative results for central adrenal
insufficiency. Low gonadotropins in thesetting of amenorrhea
or low testosterone suggest hypogonadotropic hypogonadism and
a structural lesion should be excluded. Hyperprolactinemia should
also be considered as a cause of hypogonadism because in some
cases normalization of prolactin (via medication changes or
administration of a dopamine agonist) could reverse hypogonadism.
A low IGF 1 with other pituitary deficiencies has a high probability
of representing growth hormone deficiency. If the IGF-1 is normal,
or low in the absence of other pituitary deficiencies, dynamic
testing for growth hormone deficiency is appropriate if the
patient is a candidate for growth hormone replacement. Insulin
tolerance testing should be avoided in those patients with neurologic
abnormalities who may be at risk for seizure. A less hazardous
test for growth hormone deficiency is the Arginine/GHRH stimulation
test although hypothalamic causes of growth hormone deficiency
could be missed by this test (14).
Summary
In summary,
there is increasing evidence that pituitary hormone deficiencies
occur following traumatic brain injury or subarachnoid hemorrhage.
Testing for pituitarydeficiencies is appropriate in all patientswith
a history of TBI or SAH within thefirst 6-12 months of the event.
If there are signs or symptoms suggestive of inadequate adrenal,
sex steroid, growth hormone or thyroid function, pituitary testing
should be done sooner. Longitudinal follow-up is necessary,
as not all patients sustain permanent deficiencies and some
develop hypopituitarism as a late manifestation many years after
the initial event. Prospective studies will help determine the
timing at which deficiencies develop, and provide information
regarding the benefits derived from hormone replacement during
rehabilitation from brain injury.
References
1. Agha
A, et al. J Clin Endocrinol Metab. 2004; 89:5987-92.
2. Kelly DF, et al. J Neurosurg. 2000; 93:74352.
3. Aimaretti G, et al. Clin Endocrinol (Oxf). 2004; 61:320-6.
4. Agha A, et al. Clin Endocrinol (Oxf). 2004; 60:584-91.
5. Bondanelli M, et al. J Neurotrauma. 2004; 685-96.
6. Kreitschmann-Andermahr I, et al. J Clin Endocrinol Metab.
2004; 89:4986-92.
7. Agha A, et al. J Clin Endocrinol Metab. 2004; 89:4929-36.
8. Lieberman SA, et al. J Clin Endocrinol Metab. 2001; 86:2752-6.
9. Benvenga S, et al. J Clin Endocrinol Metab. 2000; 85:1353-61.
10. Van Baalen B, et al. Disabil Rehabil. 2003; 25:9-18.
11. Hutter BO, et al. Acta Neurochir Suppl (Wien). 1999; 72:157-74.
12. Wallymahmed ME, et al. Clin Endocrinol (Oxf). 1999; 51:333-8.
13. Rosen T, Bengtsson B-A. Lancet. 1990; 336:285-8.
14. Biller BMK, et al. J Clin Endocrinol Metab. 2002; 87:2067-79.
Physiologic
Cortisol Dynamics and Cushings Syndrome in Pregnancy
Andrea L. Utz, M.D., Ph.D.
Although the
occurrence of Cushings syndrome during pregnancy is rare,
correct and expedient diagnosis is imperative due to the high
rate of maternal and fetal complications associated with the disorder.
Normal pregnancy is accompanied by an increase in cortisol concentration
and this may complicate the diagnosis of Cushings syndrome.
Knowledge of normal pregnancy cortisol levels is necessary to
separate physiologic from pathologic increases in cortisol.
Normal
Cortisol Production in Pregnancy
The progression
through pregnancy produces an increase in serum cortisol concentration
and a decrease in the responsiveness of the hypothalamic-pituitary-adrenal
(HPA) axis to exogenous glucocorticoids. High estrogen levels
of pregnancy induce an increase in cortisol binding globulin (CBG)
and this in turn increases corticotropin- releasing hormone (CRH),
adrenocorticotropin hormone (ACTH), and total cortisol levels
to maintain an adequate free cortisol concentration. Additionally,
as pregnancy progresses, there is an increase in the free fraction
of cortisol and thus an increase in the daily urinary excretion
of cortisol. The exact mechanism of the increase in free cortisol
is unknown but potential contributors include autonomous production
of CRH and/or ACTH by the placenta or a state of glucocorticoid
resistance during pregnancy. Normative reference ranges for ACTH
and serum and urine cortisol levels during the trimesters of pregnancy
do not exist. Based on preliminary studies, an approximate two
to three fold increase in these concentrations, compared to the
non-pregnant state, is apparent by the second trimester of pregnancy
and persists through the early postpartum period. Defining pathologic
states of cortisol excess or insufficiency is hindered by a lack
of well-defined reference ranges during pregnancy.
A
Study to Assess the Safety and Efficacy
of SOM 230 in Patients with Cushing's Disease
This
clinical research study is designed to investigate the
effects of an investigational medication (not approved
by the Food and Drug Administration), SOM 230, in patients
with active Cushing's disease. Primary treatment for Cushing's
disease is surgery to remove the tumor causing elevated
ACTH and cortisol levels. SOM 230 may provide an alternative
medical treatment for patients with Cushing's disease.
All adult subjects who have been diagnosed with Cushing's
disease and who have not previously undergone medical
and/or radiation therapy for the Cushing's or who have
not been cured with surgery may be eligible for this study.
There are 9 visits over one month of study participation.
Patients will receive a total of $1000 for completing
the study and SOM 230 at no charge. Those patients who
receive benefit from this medication will be offered enrollment
in an extension study where SOM 230 will be offered at
no charge until it is approved by the Food and Drug Administration.
Please
contact Karen Liebert, R.N. at 617.726.7473 or kpulaski@partners.org
|
Cushings
Syndrome During Pregnancy
The diagnosis
of Cushings syndrome is rare during pregnancy because elevated
cortisol levels often result in anovulatory menstrual cycles and
thus infertility. However, the detrimental results of hypercortisolemia
on maternal and fetal well-being underscore the importance of
early identification and treatment of Cushings syndrome
in the pregnant patient. Reported fetal complication rates include:
prematurity (43%), intrauterine growth retardation (21%), stillbirth/spontaneous
abortion/intrauterine demise (11%), and hypoadrenalism (2%). Because
pregnancy and Cushings syndrome share similar clinical signs
and symptoms, distinguishing individuals with hypercortisolism
can be difficult. For example, both states may be accompanied
by hypertension, glucose intolerance, increased weight, striae,
and amenorrhea. However, certain clinical indicators should increase
the suspicion for Cushings syndrome, such as hypokalemia,
proximal muscle weakness, and ecchymoses.
|
Table
1. Distribution of Sources of Hypercortisolemia in Pregnant
and Non-Pregnant Individuals.
|
|
Non-pregnant (%)
|
Pregnant
(%)
|
|
Pituitary
|
68
|
33
|
|
Adrenal
|
|
|
|
Adenoma
|
10
|
46
|
|
Carcinoma
|
8
|
10
|
|
Adrenal
hyperplasia
|
1
|
3
|
|
Ectopic
|
12
|
3
|
|
Other
/ undetermined
|
1
|
5
|
| Adapted
with permission from Orth et al. New England Journal of Medicine
1995; 332:791-803 and Lindsay et al. Endocrine Reviews 2005;
26:775. |
Diagnosis
When Cushings
syndrome is suspected in pregnancy, the initial test should be
measurement of 24-hour urinary cortisol excretion. Cortisol levels
higher than 3-fold the upper limit of the non-pregnant state suggest
the diagnosis of Cushings syndrome. For equivocalresults,
measurement of midnight salivary cortisol levels may indicate
abnormal circadian cortisol dynamics; however, reference ranges
for this test have not been established in pregnancy. After hypercortisolemia
is determined, the next step is localization of the source. In
non-pregnant individuals, the predominant source is a pituitary
adenoma. However, in the pregnant woman, an adrenal etiology is
more likely (see Table 1). The increase in adrenal etiology may
be due to preserved fertility in adrenal versus pituitary Cushings
syndrome. Additionally, rare cases of pregnancy-induced Cushings
syndrome have been documented and can occur as ACTHdependent
and independent forms. In the ACTH-independent cases, a
proposed mechanism is stimulation of illicit receptors on adrenal
tissue or adrenal adenomas by substances that circulate in high
concentration during pregnancy, such as hCG, LH, or estradiol,
with a subsequent increase in cortisol production. These cases
do not show abnormalities on pituitary or adrenal imaging and
there is prompt resolution of hypercortisolemia following pregnancy.
Measurement
of the ACTH level is the next step to distinguish between an adrenal
or non-adrenal source of hypercortisolemia. In the absence of
exogenous glucocorticoid use, suppressed ACTH suggests an adrenal
etiology; however, it should be noted that the normal increase
in ACTH during pregnancy may confound interpretation of the ACTH
level. In pregnant women with low-normal ACTH levels, 8 mg dexamethasone
suppression or CRH stimulation testing may help distinguish an
adrenal from a pituitary cause. In a recent report, approximately
half of pregnant patients with Cushings disease suppressed
with high-dose dexamethasone, while none of the patients with
an adrenal source showed suppression. A positive response to CRH
stimulation may also support the diagnosis of Cushings disease.
It should be noted that dexamethasone and CRH are U.S. FDA Pregnancy
Category C drugs due to a lack of animal or human studies.
If an adrenal
source is suspected, abdominal ultrasound or MRI (withoutgadolinium
contrast) is indicated, avoidingthe radiation associated with
CT scanning.Alternatively, if the ACTH is normal orelevated, a
pituitary MRI should be considered.Risks ofMRI in pregnancy have
notbeen fully addressed and therefore the risks of this test must
be weighedagainst thepotential benefits of diagnosis. Normal orequivocal
findings on the pituitary MRIraisethe suspicion for an ectopic
ACTHsource, although corticotroph adenomascan be too small tovisualize
on head MRI.In these cases, inferior petrosal sinus samplingprocedures,
with CRHstimulation, atspecialized centers have been performed
inpregnant women to confirm the locationofACTH excess. In rare
cases of pregnancyinducedCushings syndrome, a source maynot
bedetectable with imaging modalities.
Treatment
Due to the
significant risks of hypercortisolemiafor themother and the fetus,
anexpedient plan for cortisol normalization isnecessary. In most
cases, thisentails surgicalresection of the hormonally activetumor.
Close communication betweenendocrinologist, surgeon, anesthesiologistand
obstetrician is important. Transsphenoidalsurgeryis the most commonapproach
for resection of a pituitary tumorandadrenalectomy via laparoscopic
oropen resection can be performed duringpregnancy. In casesof
adrenal hyperplasia,pregnancy-induced Cushings syndrome,
orto decrease cortisol levels priorto surgicaltumor resection,
medical therapy may beimplemented using adrenal steroidogenesisinhibitors,
which are effective in decreasinghypercortisolemia. Although ketoconazoleisthe
first line therapy in the non-pregnantpatient, this medication
is contraindicatedinpregnancy due to risks of teratogenicity.Metyrapone
has been shown to be safe and effective for treating hypercortisolism
in pregnancy; however it is a U.S. FDA Pregnancy Category C drug
due to a lack of animal or human studies. It is no longer commercially
available; however, can be obtained from Novartis by calling 1-800-988-7768.
Following
definitive treatment ofhypercortisolemiawith surgery, the patientis
often adrenally insufficient, due to precedingsuppression ofthe
HPA axis byexcess glucocorticoids. Therefore, replacementglucocorticoids
are necessary; and inthe rare case of bilateral adrenalectomy,mineralocorticoid
therapy is also indicated.Hydrocortisone orprednisone are acceptable
choices for replacement because thefetus is protected from excessglucocorticoidlevels
by placental 11-ß-HSD-2metabolism of these drugs. However,dexamethasoneshould
be avoided in pregnancybecause it is not metabolized by 11-ß-HSD-2
and thus crosses the placenta. Thestandard replacement dose required
duringpregnancy has not been established, but a dose between non-pregnant
replacement and double this dose is recommended. Adjustment of
dose should be based on clinical signs and symptoms, as there
are no accurate laboratorytests to assure adequate glucocorticoid
levels. Pregnant women who have been cured of Cushings should
be educated about their adrenal insufficiency status and provided
with standard instructions for management during illness. A plan
for parenteral glucocorticoid administration is particularly important
in the pregnant population. The replacement dose should be doubled
for normal vaginal delivery and stress doses provided prior to
caesarian section with taper as clinically tolerated to a replacement
dose. Glucocorticoid replacement is considered compatible with
breastfeeding, with prednisone or hydrocortisone typically used.
The dose should be tapered and then discontinued upon HPA axis
recovery.
Summary
Normal pregnancy
is accompanied by a moderate increase in maternal cortisol levels.
In the case of a pregnancy complicated by symptoms of hypercortisolism,
the diagnosis of Cushings syndrome should be systematically
pursued. Safe and effective surgical and medical therapies for
Cushings syndrome are available for the pregnant patient
and a multidisciplinary approach necessary to improve maternal
and fetal outcome in this disorder.
References
1. Orth
DN. N Eng J Med. 1995; 332: 791-803.
2. Lindsay JR, et al. Endocrine Reviews. 2005; 26:775-99.
3. Lindsay JR, et al. J Clin Endocrinol Metab. 2005; 90:3077-83.
4. Hana V, et al. Clin Endocrinol. 2001; 54:277-81.
5. Lacroix A, et al. N Eng J Med. 1999; 341:1577-81.
SPECIAL
LECTURE
Seventh
Annual Nicholas T. Zervas, M.D. Lectureship
at the Massachusetts General Hospital
Historic Ether Dome
Tuesday,
May 16, 2006 at 12 Noon
“Sleep
Loss: A Risk Factor
for Obesity and Diabetes”
Eve
Van Cauter, Ph.D.
Professor, Department of Medicine
University of Chicago Chicago, IL
For
further information call Ivy at 617-726-3870
|
Growth
Hormone Treatment: Transitioning care from Adolescence to Adulthood
Madhusmita Misra, M.D.
The aim
of growth hormone (GH) treatment in childhood has primarily
been to optimize growth potential and adult stature in children
testing as GH deficient based on GH stimulation tests. Therapy
was traditionally stopped when growth velocity decreased to
< 1 cm per year, or at a bone age of 15 years in girls or
17 years in boys, when less than 1% of growth potential remained.
In the past few years, studies have demonstrated the need for
GH replacement in adults with GH deficiency, and have reported
improvements in body composition (decreased fat mass and increased
muscle mass), increases in bone density, reduction of cardiovascular
risk and improvement in quality of life following GH replacement.
This raises the issue of lifelong GH therapy and for many children
who believed their daily injections would end once adult height
was achieved, causes significant disappointment. One question
is whether GH treatment may be discontinued for some time in
this situation and then restarted without jeopardizing potential
beneficial effects of GH replacement. In addition, given that
criteria for GH therapy are relatively broad in childhood, it
is important to identifytruly GHdeficient individuals rather
than continue GH replacement in all young adults, some of whom
may no longer test as GH deficient. This is particularly important
because GH therapy is not without certain side effects; amongst
these the risk of developing impaired glucose tolerance and
less commonly, frank diabetes. The other important aspect is
the tremendous cost of GH replacement.
Important
considerations at the end of statural growth thus include:
1. Is the individual truly GH deficient based on repeat testing?
2. What is the appropriate dose of recombinant human GH during
the transition from childhood to adult replacement?
3. Is a period off GH replacement (GH holiday) possible
and are there subsequent effects on body composition, bone density,
cardiovascular risk and quality of life?
Is the
Individual Truly GH Deficient?
GH secretion
varies with age, and criteria for the diagnosis of GH deficiency
differ in children compared with adults. Children secrete more
GH than adults, in particular during the pubertal years, with
GH levels peaking around mid to late puberty (earlier in girls
than in boys), following which GH secretion gradually declines.
In children, a peak GH response on two provocative tests of
< 5 ng/ml suggests complete or severe GH deficiency, whereas
a peak GH response between 5-10 ng/ml is termed partialGH deficiency.
This is in contrast to adults, in whom a peak GH response of
< 3 ng/ml with the insulin tolerance test, or <4-9 ng/ml
on the GHRH-arginine test constitutes severe GH deficiency.
The cut-off for diagnosis of GH deficiency in latepuberty and
in young adults is, however,unclear. Given that GH has importanteffects
on bone andbody composition at this time of life despite growth
beingalmost complete, and because GH levels,although declining,
are still higher than inadults, it is suggested that a cut-off
of 5ng/ml rather than 3ng/ml be used todefine severe GH deficiency
in thistransition period.
Re-testing
an individual previouslydiagnosed with GH deficiency is particularlyimportant
given the diagnostic inaccuraciesassociated with GH stimulation
testing.In addition to the obvious false positivesassociatedwith
the cut-offs used inchildhood, fallacies may occur dependingon
the specificstimulation test selected,and the different GH assays
in use. Theinsulin tolerance test, which is thegoldstandard
for diagnosis of GH deficiency, israrely used in children because
of the risksfromhypoglycemia, and the GHRH-argininetest, which
is as accurate as theinsulin tolerance test inadults withouthypothalamic
dysfunction, has not provensimilarly useful in children. This
has resultedinthe use of a variety of provocativetests depending
on the age of the child,side effects, and thepreferences of
the pediatric endocrinologist. In addition todiagnostic errors
associated with theprovocative stimulus used, there are errorsobserved
related to lack of sex steroid primingprior totesting in children
who are prepubertalor in very early puberty, particularlin situations
of constitutional delay in growth and development.
In general,
teenagers most likely to continue to test severely GH deficient
are those with:
(i) Multiple pituitary hormone deficiencies
(ii) Peak GH response of < 5 ng/ml on initial testing
(iii) Structural hypothalamic-pituitaryand central nervous system
abnormalities(iv)Historyof hypothalamic-pituitaryirradiation.
Conversely,
a normal peak GH responseonrepeat testing is more likely in
individualswith:
(i)
Isolated idiopathic GH deficiency(30-70%subsequently have a
normalresponse)
(ii) Partial GH deficiency (~77% arenormal on retesting) SeeFigure
1.
Overall,
the peak GH response is normalin 20-87% of young adults who
werediagnosed with and treated for GH deficiencyin childhood.
Some endocrinologistsstop treatment inchildren with partialGH
deficiency when the 10th percentilefor height is achieved, or
puberty begins;documentation of subsequent normalgrowth velocity
in these children obviates retesting.
|
"The
recognition of a GH
deficiency syndrome in
adults necessitates identification
of adolescents and
young adults who may
warrant continuation of
treatment after statural
growth is complete."
|
Currently,discontinuation
of treatmentand reassessment of GH secretory status isnecessary
before adult replacement can beinitiated. Discontinuation of
GH treatmentfor a period ofthree months is sufficient; reports
exist of recovery of the GH axiseven four weeks after interruption
of GH therapy. It is interesting to note that at least one study
has demonstrated normalized GH responses to stimulation testing
in 29% of children even during daily GH replacement.
The European
Society of PediatricEndocrinology has recently proposed newguidelines
based on serum IGF-I levels and GHstimulation testing (insulin
tolerancetest, arginine or glucagon). Continuationof GH therapy
without interruption is suggested for teenagers with severe
congenital or acquired hypopituitarism and multiple hormonal
deficiencies. In adolescents with high likelihood of severe
GH deficiency, measuring IGF-I after a month of discontinuing
GH, and restarting GH treatment if serum IGF-I is < -2 S.D.s
is recommended. For adolescents with IGF-I levels > -2 S.D.s,
a GH stimulation test is suggested, withGH treatment to be restarted
inpatients with a low peak GH response. Foradolescents with
low likelihood of severeGH deficiency, both serum IGF-I and
GH stimulation testing are recommended, with GH therapy to be
restarted if IGF-I and peak GH response are low, to be stopped
if both are normal, and further follow up suggestedif results
are discordant.
What
is the Ideal Dose of rhGH DuringtheTransition from Adolescent
to Adult GHReplacement?
This is
an important question, which hasnot yet been fully addressed.
Based onhigher GH concentrations in children andadolescentscompared
with adults, the replacement dose in children is higher (30-40
mcg/kg/day or 0.22-0.30 mg/kg/week)compared with adults (2-12
mcg/kg/day). The optimal dose during the transitionfrom adolescent
to adult replacement is likely somewhere in between, given that
GH concentrations gradually decrease after puberty to adult
levels. At least one study has suggested that a higher dose
(25 mcg/kg/day) may have greater beneficial effects compared
with a smaller dose (12.5 mcg/kg/day), although not all studies
demonstrate a dose effect. Dose titration based on IGF-I levels
for age is an alternative method of determining the optimum
GH dose. This is even more important given the recently demonstrated
differences in IGF-I levels depending on gender, with lower
levels of IGF-I in women than in men.
Is a
Drug Holiday Possible and How Long Should This Last?
Benefits
of a drug holiday include temporary freedom from daily injections,
and for the young adult to feel that plans made in childhood
are being honored. Their sense of autonomy is maintained, and
this period off GH allows for re-testing to be performed. For
individuals that are not GH deficient on re-testing, there is
no indication for restarting therapy. However, in individuals
continuing to be severely GH deficient, the question arises
as to when replacement should be resumed.
In addition
to results of stimulation testing, this may be influenced by
whether symptoms of GH deficiency develop in the young adult.
Early development of clinical features makes the decision to
re-start therapy relatively simple. Features of adult GH deficiency
include an increase in fat mass, a decrease in muscle mass resulting
in decreased strength and exercise capacity, as well as a deterioration
of quality of life.
However,
an insidious development of symptoms may cause the individual
to miss early features of adult GH deficiency, and this may
be exaggerated by a subconscious reluctance to return to daily
injections. In addition, some of the deleterious effects of
GHD in adults, such as osteoporosis and increased cardiovascular
risk are silent until fractures or cardiovascular events occur.
Another major issue is that patients this age are often lost
to follow up. They may no longer feel comfortable in a pediatricians
office, yet not have an established relationship with an adult
care provider familiar with the use of GH. Individuals with
multiple pituitary hormone deficits, those with evidence of
severe GH deficiency, associated structural central nervous
system abnormalities, and past history of irradiation are more
likely than others to manifest the adult GH deficiency syndrome
and be seen by an adult endocrinologist.
|
"Discontinuation
of
therapy for a period of
one to three months is
advisable prior to
retesting."
|
Of importance
is the effect of GH on bone and body composition in the young
adult. Healthy adolescents 17-21 years old exhibit increased
lean body mass and handgrip strength over a two-year period
but this does not occur in untreated GH deficient adolescents.
Small studies in adolescents treated with GH during adulthood
have demonstrated that fat mass increases by about 5% and muscle
mass decreases commensurately within a year following discontinuation
of GH, and reductions occur in muscle strength, muscle size
and fiber area. Increases in trunk fat have been reported in
GH deficient adolescents following discontinuation of GH therapy
(Figure 2).
Adolescence
and young adulthood are the periods of life when bone mass accrual
is maximal, culminating in achievement of peak bone mass. This
raises concern that cessation of GH replacement may result in
permanent deficits, particularly of bone mass, resulting in
increased fracture risk in later life. A recent study of 40
GH deficient adolescents found no beneficial effects of GHreplacement
at a dose of 20mcg/kg/day, (i.e. about half the pediatric GH
replacement dose), versus placebo on bone density, body composition,
cardiac function, muscle strength, carbohydrate or lipid metabolism,
or quality of life over a two year period. A trend towards lower
bone density at the lumbar spine was, however, noted in the
group receiving placebo. A significant difference may have been
evident with a larger study, with a higher retention rate (only
two thirds of the subjects completed the study) or with higher
doses. Although continued increase in bone mass has been demonstrated
up to two years after discontinuation of GH therapy, investigators
have reported that attainment of peak bone mass is slower and
ultimate peak bone mass lower than in controls, with rapid decline
in bone density occurring two years after attainment of peak
bone mass.
Beneficial
effects on metabolic profiles and specific quality of life measures
have been reported in other studies in GH deficient adolescents
continued on GH after completion of growth (Figure 3). Larger
studies are awaited to provide definitive information regarding
the safety and duration of a drug holiday in older teenagers
and young adults.

Conclusion
The recognition
of a GH deficiency syndrome in adults necessitates identification
of adolescents and young adults who may warrant continuation
of treatment after statural growth is complete. Discontinuation
of therapy for a period of one to three months is advisable
prior to re-testing. A peak GH response of < 5 ng/ml suggests
the need for adult GH replacement therapy in transitional doses
to begin with, to be gradually weaned to adult doses over time.
Rapid resumption of GH replacement is especially recommended
in individuals with clinical evidence of adult GH deficiency.
However, complete reliance on symptoms alone may delay restarting
therapy because there are no early symptoms of some features
of GHD, or the onset of symptoms may be insidious, and because
of the risk of loss to follow up. A drug holiday is possible,
but the duration of this period off GH should be balanced against
risks of impaired bone mass accrual, increases in fat mass and
decreases in muscle mass leading to poor muscle strength, increased
cardiovascular risk and impaired lipid profiles, and a deterioration
in quality of life. Current data suggest that the duration of
discontinuation of GH therapy should not last longer than two
years pending further data. Interaction between the pediatric
and adult endocrinologists during the transition period is crucial
to determine an optimal management plan for each young adult.
References
1. Allen
DB. Pediatrics. 1999; 104(4 Pt 2): 1004-10.
2. Attanasio AF, et al. J Clin Endocrinol Metab. 2005; 90:4525-9.
3. Clayton PE, et al. Eur J Endocrinal. 2005; 152: 165:165-70.
4. Mauras N, et al. J Clin Endocrinol Metab. 2005; 90:3946-50
5. Saggese G, et al. J Endocrinol Invest. 2004; 7:596-602.
6. Shalet S. Horm Res 2004; 62 (suppl 4):15-22.
MASSACHUSETTS
GENERAL HOSPITAL
Acromegaly Patient Education Day
|
Dr.
Karen K. Miller describes
clinical approaches to
acromegaly.

|

Dr.
Beverly M.K. Biller explains the anatomy
and physiology of the pituitary gland.
Nurses
Karen Liebert and Karen Szczesiul
answer patient questions about
medical treatment of acromegaly.

|
On April
25, 2005, the Massachusetts General Hospital Neuroendocrine
Clinical Center hosted patients and their guests for an informative
Acromegaly Patient Education Day.
Attendees
from 15 states learned about many aspects of the disorder from
endocrinologists, nurses and an expert pituitary surgeon.
Slide presentations
and a video of an actual transsphenoidal pituitary operation
were highlighted by question and answer periods.
Patients
with acromegaly shared their stories, providing a unique opportunity
for patients with this rare disorder to meet other people with
the same condition.
|

Neurosurgeon
Dr. Brooke Swearingen explains
transsphenoidal surgery to the attendees.
|
Neuroendocrine
Unit Chief, Dr. Anne Klibanski,
describes the clinical features of acromegaly and
how the condition is diagnosed.

|
Excellent
overview easy to understand
|
|
|
|
|
|
|
|
Absolutely
outstanding
great explanation of medications
and side effects |
|
|
I
never knew a surgeon could
have a sense of humor. |
|
|
|
|
|
|
|
Invaluable
to meet other
patients with acromegaly |
RESEARCH
STUDIES AVAILABLE
Physicians
at the Neuroendocrine Clinical Center at Massachusetts General
Hospital are conducting several exciting research studies aimed
at understanding and addressing medical issues related to pituitary
disorders and learning more about the mechanisms of anorexia
nervosa and applying novel treatments that will help improve
future clinical treatments.
We are actively
recruiting participants for several research studies described
on this site and we hope that you will consider participating.
We encourage you to investigate the educational material provided
regarding pituitary disorders, and please do not hesitate to
contact us if you would like further information.
Patients
may qualify for research studies in the Neuroendocrine Clinical
Center. We are currently accepting the following categories
of patients for screening to determine study eligibility. Depending on the study, subjects may receive
free testing, medication and/or stipends.
[ see Neuroendocrine Links for more
information ]
|
SUBJECTS
|
STUDIES
|
CONTACT
617-726-3870
|
|
Newly
diagnosed acromegaly patients
|
·
Evaluating
preoperative medical treatments
|
Karen
Pulaski-Liebert, R.N.
Dr.
Beverly M.K. Biller
|
|
Patients
with Cushing’s Syndrome
|
·
Evaluating
a potential new medical therapy
|
Karen
Pulaski-Liebert, R.N.
Dr.
Beverly M.K. Biller
|
|
Patients
with history of cured acromegaly with or without hypopituitarism
|
· | |