The Journal of Clinical Endocrinology & Metabolism Vol. 82, No. 2 514-517
Copyright © 1997 by The Endocrine Society
Acute Effects of Bromocriptine, Cyproheptadine, and Valproic Acid on Plasma Adrenocorticotropin Secretion in Nelsons Syndrome
Leilani B. Mercado-Asis1,
Jack A. Yanovski2,
Howard L. Tracer3,
Constance L. Chik4 and
Gordon B. Cutler, Jr.2
Developmental Endocrinology Branch, National Institute of Child
Health and Human Development, and the Office of the Director, Warren
Grant Magnuson Clinical Center, National Institutes of Health,
Bethesda, Maryland 20892
Address all correspondence and requests for reprints to: Gordon B. Cutler, Jr., M.D., Developmental Endocrinology Branch, National Institute of Child Health and Human Development, Section on Developmental Endocrinology, Building 10, Room 10N262, 10 Center Drive, MSC 1862, Bethesda, Maryland 20892-1862.
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Abstract
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Previous studies have found that bromocriptine, cyproheptadine,
and valproic acid can reduce ACTH secretion in Nelsons syndrome, but
none of these agents has achieved widespread use due to their failure
to normalize ACTH in most patients. The current study was undertaken to
determine whether these three agents, which act through different
mechanisms, decrease plasma ACTH synergistically when administered
together. Six adult female patients (mean age, 41 yr) with Nelsons
syndrome were studied. ACTH was measured every 20 min for 8 h,
2 h before and 6 h after each of the following six
treatments: placebo, bromocriptine (2.5 mg), cyproheptadine (8 mg),
valproic acid (1 g), cyproheptadine plus valproic acid, and the
combination of all three drugs. The sequence of treatments was
determined randomly, and there was an interval of at least 2 days
between each treatment. The hourly ACTH values were averaged, and the
percent maximal suppression of plasma ACTH, relative to the baseline
values before drug administration, was compared among the six
treatments. Basal plasma ACTH levels in the six patients ranged from
403324 pmol/L (normal range, 18). The percent maximal suppression
of ACTH after administration of placebo (6 ± 11%),
cyproheptadine (17 ± 15%), valproic acid (37 ± 10%), or
the combination of cyproheptadine and valproic acid (19 ± 14%)
did not achieve statistical significance. Bromocriptine, on the other
hand, caused a significant decrease in plasma ACTH (52 ± 8%;
P < 0.05), as did the combination of
bromocriptine, cyproheptadine, and valproic acid (58 ± 12%;
P < 0.05). However, the combined effect of the
three drugs did not significantly exceed the effect of bromocriptine
alone. We conclude that at the doses studied, bromocriptine had the
greatest acute effect in suppressing ACTH secretion in Nelsons
syndrome, and that combined administration with valproic acid and
cyproheptadine did not further increase this acute ACTH-suppressive
effect.
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Introduction
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NELSON AND colleagues in 1958 (1) described
the syndrome of hyperpigmentation, marked ACTH hypersecretion, and an
enlarging pituitary tumor after bilateral adrenalectomy for Cushings
disease. Current treatment for this condition is transsphenoidal
resection of the tumor and/or irradiation (2, 3). Although most
patients respond well to this approach, a minority have progressive
tumor growth and rising ACTH levels (4, 5, 6).
An alternative management approach for such patients is medical
treatment to suppress ACTH (7). Valproic acid (8), cyproheptadine (9),
and bromocriptine (10, 11) have each been shown to reduce ACTH in some
patients with Nelsons syndrome. None of these agents has achieved
widespread use, however, due to the limited data on their abilities to
normalize ACTH secretion.
The distinct mechanisms of action of bromocriptine, cyproheptadine, and
valproic acid led us to hypothesize that they might have additive or
synergistic effects in suppressing plasma ACTH. Bromocriptine, a
dopamine agonist, is thought to exert its effects through pituitary
dopamine receptors (10, 11, 12, 13, 14, 15, 16, 17, 18). Cyproheptadine, a serotonin antagonist,
was originally proposed to suppress ACTH through a hypothalamic site of
action (19, 20, 21, 22, 23), but may also have direct effects on ACTH-secreting
tumor cells (12, 22, 24, 25, 26). Valproic acid, an inhibitor of
-aminobutyric acid reuptake, is presumed to act by enhancing
-aminobutyric acid inhibition of hypothalamic CRH release (8, 27, 28, 29, 30, 31, 32, 33, 34, 35). To evaluate the potential synergism of multidrug regimens in
the treatment of Nelsons syndrome, we determined the acute effects of
single doses of bromocriptine, cyproheptadine, and valproic acid,
separately and in combination, in patients with Nelsons syndrome.
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Materials and Methods
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Clinical features of the patients
Six women (mean age, 41 yr; range, 2959 yr) were studied 225
yr after bilateral adrenalectomy for Cushings disease. All six had a
radiologically detected pituitary adenoma at presentation, which was
pathologically confirmed as corticotropinoma in the five patients who
underwent surgery (Table 1
). None had evidence of
ectopic secretion of ACTH or CRH. All patients were diagnosed as having
Nelsons syndrome on the basis of hyperpigmentation and elevated basal
plasma ACTH levels at the time of study. When enrolled in this study,
patients 1, 4, 5, and 6 had magnetic resonance imaging evidence of
extrasellar extension of their pituitary tumor, whereas patients 2 and
3 had no obvious evidence of residual pituitary tumor. Five subjects
had undergone transsphenoidal surgery (patients 1, 2, 4, 5, and 6) or
pituitary irradiation (patients 1, 2, 3, 5, and 6) 112 yr before
study, and all except patient 2 were receiving treatment for secondary
hypothyroidism, hypogonadism, or diabetes insipidus. The protocol was
approved by the institutional review board of the NICHHD, and informed
consent was obtained from each subject.
Protocol
Data were collected for six different test periods: placebo,
bromocriptine (2.5 mg), cyproheptadine (8 mg), valproic acid (1 g), the
combination of cyproheptadine (8 mg) and valproic acid (1 g), and the
combination of cyproheptadine (8 mg), valproic acid (1 g), and
bromocriptine (2.5 mg). The sequence of the six tests was randomized,
and the interval between tests was at least 2 days. The cortisol
maintenance dose was withheld on test days until after the 8-h sampling
period (1600 h). Blood samples for determination of plasma ACTH were
collected every 20 min for 8 h starting at 0800 h (2 h before
and 6 h after administration of the test medication). The basal
ACTH level for each test period was determined by averaging the seven
successive ACTH measurements obtained every 20 min between 08001000 h
before administration of the study medication.
Plasma ACTH was measured by polyclonal RIA after extraction (36). The
sensitivity of the ACTH assay ranged from 0.92.2 pmol/L. The intra-
and interassay variabilities were 712% and 1225%, respectively.
All samples from a given day were measured in the same assay.
Statistical analysis
Data are presented as the mean ± SEM. To
analyze drug effects on ACTH, for each study medication we first
determined the mean ACTH level during the initial 2 h before drug
administration (the average of the seven successive baseline ACTH
values obtained every 20 min between 08001000 h) and then found the
hourly mean ACTH (the average of the three ACTH values obtained during
that hour) for each of the 6 h after administration of the study
medication. The percent maximal suppression (PMS) of ACTH was
determined from the lowest mean hourly ACTH level during the 6 h
after drug administration. PMS data were subjected to an
arc-sine-square root transformation before one-way ANOVA with repeated
measures. Post-hoc paired Fishers least significant
differences test was used to determine significance among the various
medications using the Bonferroni adjustment for multiple comparisons.
Nominal P values are reported.
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Results
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ANOVA with repeated measures demonstrated a significant effect of
medication (Fig. 1
; P < 0.05).
Administration of placebo caused no significant change in plasma ACTH
(PMS, 6 ± 11%), whereas bromocriptine caused a significant
decrease in plasma ACTH (52 ± 8%; P < 0.05
vs. placebo). The maximal decrease in plasma ACTH did not
achieve statistical significance after administration of cyproheptadine
(17 ± 15%), valproic acid (37 ± 10%), or the combination
of cyproheptadine and valproic acid (19 ± 14%). Although the
greatest suppression of plasma ACTH was observed when all three
medications (bromocriptine, cyproheptadine, and valproic acid) were
given together (58 ± 12%; P < 0.05
vs. placebo), the difference between the suppression induced
by bromocriptine alone and that induced by the combination of all three
agents was not statistically significant. The time of maximal ACTH
suppression was 4.8 ± 0.5 h (mean ± SEM)
after bromocriptine administration and 3.8 ± 0.7 h after the
administration of all three drugs (P = NS).

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Figure 1. PMS of plasma ACTH (relative to the mean
level at 08001000 h) in six patients with Nelsons syndrome after
single doses of bromocriptine (2.5 mg), cyproheptadine (8 mg), valproic
acid (1 g), cyproheptadine plus valproic acid (Cypro + Valpro), or the
combination of all three drugs. Solid bars represent the
mean ± SEM. Each subjects data points are indicated
by the symbols to the left of each solid bar. *,
P < 0.05 vs. placebo treatment.
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Adverse effects of the study drugs included moderate orthostatic
hypotension in five patients (patients 15) after bromocriptine
ingestion. Patient 4 had severe dizziness, nausea, and vomiting in
response to the combination of the three drugs, and patient 2
experienced sleepiness.
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Discussion
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Among the three drugs evaluated, each of which has been shown in
previous reports to suppress ACTH secretion in patients with Nelsons
syndrome, only bromocriptine (2.5 mg) suppressed ACTH levels acutely at
the dose used in this study. Our results support earlier observations
on the suppressive effects of bromocriptine on ACTH secretion (10, 11, 12, 13, 14, 15, 16, 17, 18),
but did not demonstrate the efficacy of cyproheptadine (19, 20, 21, 22, 23, 24, 25, 26) or
valproic acid (27, 28, 29, 30, 31, 32, 33, 34, 35). Moreover, contrary to our hypothesis, the
combination of bromocriptine, cyproheptadine, and valproic acid did not
produce greater acute ACTH-suppressive effects than bromocriptine
alone. Thus, this acute, single dose study did not provide a rationale
for the combined use of these agents in the management of Nelsons
syndrome.
Although this study found no synergism among these drugs when
administered acutely, it remains possible that additive or synergistic
effects might be observed in longer term studies or with different
dosing regimens. For example, Krieger and colleagues suggested that the
maximal response to cyproheptadine requires at least 3 weeks of
treatment at a dose of 24 mg/day (9, 20, 37). Thus, the issue of
whether the combined use of these drugs for longer periods might have
additive or synergistic effects will have to be resolved through longer
term studies.
The patient with Nelsons syndrome who is refractory to
transsphenoidal surgery and pituitary irradiation remains a difficult
treatment problem. For these patients, continued research is needed to
develop a medical therapy that approaches the effectiveness of the
medical treatments for prolactinomas (38) and somatotroph adenomas
(39).
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Footnotes
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1 Current address: Section of Endocrinology and Metabolism, Department
of Medicine, Faculty of Medicine and Surgery, University of Santo
Tomas, Espana, Manila, Philippines. 
2 Commissioned officer, USPHS. 
3 Current address: 8300 Corporate Drive, Landover, Maryland
20785. 
4 Current address: Room 362, HMRC, Division of Endocrinology and
Metabolism, Department of Medicine, University of Alberta, Edmonton,
Alberta Canada T6G 2S2. 
Received July 15, 1996.
Revised September 19, 1996.
Accepted October 10, 1996.
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