Hypophysiotropic hormone testing in a patient with hypothalamic hypopituitarism.

A 59-year-old woman with metastatic breast carcinoma presented with weight loss, vomiting, and polyuria. Basal endocrine testing revealed low levels of thyroxine, cortisol, and gonadotropins, and the presence of diabetes insipidus. Direct stimulation of the pituitary with hypophysiotropic hormones indicated intact pituitary reserve. Insulin-induced hypoglycemia, however, failed to increase plasma cortisol or growth hormone levels significantly. On computed tomographic scanning, a lesion was found in the area of the hypothalamus. Thus, a functional abnormality of the hypothalamic-pituitary axis causing clinically significant hypothalamic hypopituitarism was not clearly apparent following administration of hypothalamic releasing factors but was demonstrable with indirect stimulation via insulin-induced hypoglycemia. Insulin-induced hypoglycemia remains an important diagnostic test in the evaluation of hypopituitarism.