CLINICAL EXPERIENCE WITH THE THYROTROPHIN RELEASING HORMONE (TRH) STIMULATION TEST IN PATIENTS WITH THYROID, PITUITARY AND HYPOTHALAMIC DISORDERS

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Abstract
The clinical value of a standardized iv TRH-stimulation test was studied in 96 patients with thyroid, pituitary and hypothalamic disorders. A lack of TSH-response to TRH, 50–200 μg iv was observed in 38 patients with overt hyperthyroidism. Nor was there any response in three clinically euthyroid patients with suspected hyperthyroidism, normal routine thyroid tests and failing suppressibility after the administration of T3 or T4. Twenty-one patients with primary hypothyroidism had high basal TSH-levels (mean ± sem = 85.6 ±12 μU/ml). Furthermore, a prolonged TSH-response was characteristic of this group. No correlation was found between the degrees of clinical hypofunction and basal TSH or TSH-responses. Nine patients with hypothyroidism secondary to pituitary lesions did not respond to TRH-stimulation. In clinically euthyroid patients with pituitary chromophobe adenomas, two exhibited normal and five impaired TSH-responses. Nine out of 12 patients with active acromegaly showed no or impaired TSH-response, and, on an average, there was a slight increase in the serum TSH at 20 minutes in response to TRH. A several-fold increase in serum STH occurred after TRH in five acromegalic patients. A normal TSH-response was obtained in four of six patients with hypothalamic lesions. In conclusion, the TRH-stimulation test is of special clinical value in patients with hyperthyroidism (no response), in discriminating between primary and secondary hypothyroidism and in assessing the functional pituitary TSH-reserve in pituitary and hypothalamic lesions.

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