Abnormalities in the Release of TSH in Response to Thyrotropin-Releasing Hormone (TRH) in Patients with Disorders of the Pituitary, Hypothalamus and Basal Ganglia

The availability of synthetic TRH has permitted studies of TSH release in various disorders of the hypothalamic-pituitary axis. Forty-five patients with disorders of the pituitary, hypothalamus or basal ganglia were studied. The TSH response to 400 μg intravenous TRH was normal in all but two of 19 acromegalics, normal or high in 6 patients with chromophobe adenomas, low or undetectable in 7 patients with panhypopituitarism, normal or low in 3 patients with galactorrhea and amenorrhea and in 5 with parkinsonism, and normal or markedly elevated in 3 patients with hypothalamic hypothyroidism. Unexpectedly, plasma GH also rose significantly after TRH administration in 10 of 11 untreated acromegalics with elevated fasting GH levels. These results demonstrate the usefulness of TRH in characterizing the location and extent of lesions in the hypothalamic-pituitary axis, and suggest those therapeutic measures, including the administration of certain releasing hormones, which may be employed to treat certain tertiary or hypothalamic endocrine disorders.