Paradoxical responses of plasma cortisol, adrenocorticotropic hormone and growth hormone to thyrotropin-releasing hormone and luteinizing-hormone-releasing hormone in anorexia nervosa patients

Harmful effects of functional hypercortisolism: a working hypothesis

Functional hypercortisolism (FH) is caused by conditions able to chronically activate hypothalamic-pituitary-adrenal axis and usually occurs in cases of major depression, anorexia nervosa, bulimia nervosa, alcoholism, diabetes mellitus, simple obesity, polycystic ovary syndrome, obstructive sleep apnea syndrome, panic disorder, generalized anxiety disorder, shift work, and end-stage renal disease. Most of these states belong to pseudo-Cushing disease, a condition which is difficult to distinguish from Cushing's syndrome and characterized not only by biochemical findings but also by objective ones that can be attributed to hypercortisolism (e.g., striae rubrae, central obesity, skin atrophy, easy bruising, etc.). This hormonal imbalance, although reversible and generally mild, could mediate some systemic complications, mainly but not only of a metabolic/cardiovascular nature, which are present in these states and are largely the same as those present in Cushing's syndrome. In this review we aim to discuss the evidence suggesting the emerging negative role for FH.

Subpopulations of somatotropes with differing intracellular calcium concentration responses to secretagogues

Multiple secretagogues stimulate the release of growth hormone (GH). The present studies examined the ability of chicken somatotropes to respond to GH secretagogues with increased intracellular calcium concentrations ([Ca2+]i). It was hypothesized that there are subsets of the somatotrope population with different responsiveness to the various secretagogues. Somatotropes were identified and distinguished from other adenohypophyseal cells, by their unique ability to respond to GH-releasing hormone with increased [Ca2+]i with immunocytochemistry used as a post-hoc confirmatory test. Large increases in [Ca2+]i (222 +/- 16 nM) were evoked by thyrotropin-releasing hormone in only 73% of the somatotropes. Similarly, [Ca2+]i was increased by perifusion with pituitary adenylate cyclase-activating peptide in 85% and by leptin but only in 51% of somatotropes. Ghrelin acutely increased [Ca2+]i in only 21% of somatotropes. Perfusion with gonadotropin-releasing hormone elevated [Ca2+]i, but in only 40% of somatotropes. The kinetics of calcium transients and the magnitude of the response differed from those observed in the presumptive gonadotropes. It is concluded that there are subsets of the somatotrope population in the anterior pituitary gland with differences in their ability to respond to various secretagogues.

Thyrotropin-releasing hormone in critical illness: from a dopamine-dependent test to a strategy for increasing low serum triiodothyronine, prolactin, and growth hormone concentrations

OBJECTIVE

The aim of this study was to examine the effect of dopamine infusion on the thyrotropin (TSH), thyroid hormone, prolactin, and growth hormone responses to thyrotropin-releasing hormone (TRH) in critically ill patients.

DESIGN

Prospective, randomized, controlled, open-labeled clinical study.

SETTING

The intensive care unit, University Hospital Gasthuisberg, Leuven, over a 1-month period.

PATIENTS AND INTERVENTIONS

In 15 critically ill patients receiving dopamine treatment (5 micrograms/kg/min) for a mean of 43.3 +/- 1.2 (SEM) hrs after trauma or cardiac surgery, we studied the TSH, thyroid hormone, prolactin, and growth hormone responses to the administration of two consecutive intravenous TRH boluses of 200 micrograms, with a 6-hr interval. The dopamine infusion was continued in the control group and discontinued in the study group. Serum concentrations of TSH, prolactin, and growth hormone were measured before and 20, 40, 60, and 120 mins after TRH administration. Serum concentrations of thyroxine (T4), triiodothyronine (T3), reverse T3, and thyroid hormone binding globulin were determined before and 120 mins after each TRH injection.

MEASUREMENTS AND MAIN RESULTS

There was a > 100-fold interindividual variation in the baseline TSH concentration and in the TSH peak value after TRH administration. Two consecutive doses of TRH evoked a mean 16% increase in serum T4 concentration (p = .003) and a mean 47% increase in T3 (p = .001), whereas serum reverse T3 and thyroid hormone binding globulin values remain unaltered. Each of the TRH boluses increased serum growth hormone concentrations in the continued dopamine and discontinued dopamine groups, by a median of 60% (p = .001) and 68% (p = .001), respectively. Three hours after dopamine withdrawal, there was a three-fold increase of the peak TSH response (p = .001), a higher T3 response (p = .01), and a ten-fold increase of the peak prolactin value (p = .001) in response to TRH administration.

CONCLUSIONS

The TSH response to TRH administration in critical illness presents a striking interindividual variation and dopamine dependent. Repeated TRH administration results in a repetitive increase of TSH, prolactin, growth hormone, T4, and T3, without increasing reverse T3. These observations point toward a potential for TRH as a strategy for reversing the euthyroid sick syndrome, growth hormone deficiency, and immune dysfunction associated with critical illness.

Is anorexia nervosa a neuropsychological disease?

Evidence for central nervous system, and more particularly cortical, etiology of anorexia nervosa is reviewed. Topics covered are neuropsychiatric comorbidity, inheritance patterns, the neurobiology of body-image disturbance and of the eating function, perinatal and alcoholic insult to the brain, neurochemical and neuroelectric disturbance, anatomic and metabolic brain imaging, and neuropsychological impairment. It is concluded that there is indeed an important neuropsychological etiological dimension to anorexia nervosa. The profile most frequently associated with anorexia nervosa is right posterior hypometabolism, followed by right anterior hypermetabolism, both associated with right-sided abnormal electroencephalogram spiking. It is also proposed that bulimia consists of a "positive" neurological subtype and that restricting anorexia represents a "negative" neurological subtype. Priorities for further research into anorexia nervosa are specified to include twin adoption studies, brain electrical topography studies, postmortem histological studies, and experimentally inspired neuropsychological studies.

Triiodothyronine administration reduces serum growth hormone levels and growth hormone responses to thyrotropin-releasing hormone in patients with anorexia nervosa

The aim of this study was to test the hypothesis that low serum T3 concentrations may promote an abnormal growth hormone (GH) response to thyrotropin-releasing hormone (TRH) in patients with anorexia nervosa. Eight anorexic women and two anorexic men, ages 15-25 years, with low free T3 circulating levels (mean +/- SEM = 2.8 +/- 0.3 pmol/l) were studied. A TRH test (200 micrograms IV) was carried out under basal conditions and repeated following treatment with oral T3 (1.5 micrograms/kg BW/day) for eight days. Following T3 administration, GH levels dropped significantly from a baseline of 7.1 +/- 1.3 micrograms/l to 3.1 +/- 0.7 micrograms/l (p less than 0.02), as did GH peak responses to TRH (9.0 +/- 1.0 micrograms/l vs 4.4 +/- 0.8 micrograms/l, p less than 0.01). ANOVA and analysis of area under the curve (AUC) confirmed that after T3 treatment there was a significant reduction in TRH-induced GH release in these patients (GH AUC: 902 +/- 132 micrograms/l vs. 456 +/- 91 micrograms/l, p less than 0.02). TSH responses to TRH, which were normal prior to T3 treatment, completely disappeared following it, and PRL responses to TRH also were diminished. Although our experimental approach does not permit a conclusion that low T3 levels were the primary reason for these changes, the data support the theory that low T3 circulating levels may facilitate abnormal GH secretion and the GH-releasing activity of intravenous TRH.