Thyrotropin-Releasing Hormone as a Pituitary-Function Indicator

Abstract

Pituitary thyrotropin reserves were tested with intravenous injections of 500μg of lopremone (synthetic thyrotropin-releasing hormone) in eight normal subjects, ten patients with complete hypopituitarism, and ten with incomplete hypopituitarism. Normal subjects had a mean basal thyrotropin-stimulating hormone level of 2.3μ± 1.8μU/ml and attained a mean maximal thyrotropin-stimulating hormone level of 19.8μ ± 8.2μU/ml 20 to 30 minutes after injection; no marked response occurred in patients with complete hypopituitarism. Of the incomplete hypopituitarism group, two had subnormal responses and were clinically hypothyroid. The others, clinically euthyroid, had normal responses compared to normal subjects of similar ages. Growth hormone reserve in this group was first to show impairment, whereas adrenocorticotropic hormone and thyrotropin-stimulating hormone reserves were last affected. The lopremone stimulation test is useful and specific in evaluating pituitary thyrotropin reserve.