A rare form of hypothyroidism.

Secondary hypothyroidism is extremely rare. In the majority of cases, there is a genetic (gene mutations) or structural (mass effect or infiltration) basis for central hypothyroidism, and there is simultaneous deficiency of other adenohypophysial hormones. Isolated deficiency of thyrotropin is even rarer. This report features the case of a woman who had isolated thyrotropin deficiency, with the remainder of the anterior pituitary hormones being normal. The various causes of central hypothyroidism and the role of the thyrotropin-releasing hormone test are briefly described.