Hypopituitarism: A Study of Growth Hormone and Other Endocrine Functions

Abstract

Pituitary function was evaluated in 25 adults with evidence of hypopituitarism or enlargement of the sella turcica. Growth hormone [GH] secretory function was measured by radioimmunoassay of plasma samples taken before and after insulin-induced hypoglycemia, in a standardized test of GH reserve. All patients exhibited significant defects in GH secretion as indicated by the failure of this hormone to rise to normal levels in response to hypoglycemia. The order of frequency of hormonal loss was: GH, gonado-tropin, adrenocorticotropic hormone, thyroid stimulating hormone. No pattern of deficiency was characteristic for any particular etiology of hypopituitarism. One patient with asymptomatic enlargement of the sella turcica, discovered accidentally, had an isolated loss of GH secretory capacity. Two patients in the series demonstrated intrinsic deficiency of thyroid, as well as pituitary secretion, and both had elevated titers of antithyroid antibodies. This study represents the 1st direct evaluation, by radioimmunoassay, of GH function in a series of hypopituitary adults. It demonstrates a remarkably high prevalence of GH loss, and suggests that the GH response to hypoglycemia may be one of the most sensitive tests for the diagnosis of hypopituitarism.