HYPOTHALAMIC ENDOCRINE DYSFUNCTION IN ANOREXIA NERVOSA

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Abstract
The hypothalamic-pituitary function of 21 women with anorexia nervosa, aged 15-34 yr, was studied. The tests included, in addition to the usual tests of thyroid function, a TRH [tyyrotropin releasing hormone] stimulation test with 200 .mu.g of synthetic TRH given i.v.; the response of serum immunoreactive growth hormone [GH] to insulin; and the diurnal variation and response of plasma cortisol to insulin hypoglycemia. The mean serum TSH [thyrotropin] level of the patients was higher than that of healthy controls. The mean maximal increment of TSH after TRH was similar in the patients and the controls. However, 18 of the patients but none of the controls showed a delayed TSH-response to TRH, i.e., the TSH-level at 60 min was higher than that recorded 20 min after TRH. Four of the patients had a low free thyroxine index, computed from the PBI [protein-bound iodine] and T3 [triiodothyronine] Sephadex uptake values, and 3 of these were clinically hypothyroid. The means for PBI, T4 [thyroxine] and the free thyroxine index were all significantly below the means for the controls. The basal serum GH levels were increased in 9 out of 17 patients. In 4 of these an inadequate response to insulin or to glucagon was found. In 5 out of the 8 patients with normal basal GH levels a normal response was found, whereas the remaining 3 showed a subnormal response. The serum GH level was correlated with the degree of weight loss but not with the serum albumin concentration. Plasma cortisol at 08.00 was increased in 9 patients and the diurnal variation was inadequate in 6. Four patients showed a subnormal response to insulin-induced hypoglycemia, and 2 out of 5 patients tested failed to show adequate suppression of plasma cortisol after 1 mg of dexamethasone. Dysfunction of the hypothalamic-pituitary axis is common in anorexia nervosa. A delayed TSH-response to TRH, compatible with hypothalamic dysfunction, seems to be an almost consistent feature of the disorder, and in some of the patients even clinical hypothalamic hypothyroidism may be evident.

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