Acromegaly with normal growth-hormone levels and pituitary histology. Case report.

In rare cases, acromegalic patients have normal basal concentrations of growth hormone, and their acromegaly results from abnormal growth-hormone secretory patterns. A patient is reported with the clinical features of acromegaly, who had elevated somatomedin levels and an enlarged sella turcica, but whose serum growth-hormone levels on continuous monitoring were in the normal range, with levels of 2.8 to 8.9 ng/ml. Dynamic studies of growth hormone revealed normal responses to hypo- and hyperglycemia, but abnormal responses to L-dopa and thyroid-releasing hormone. At surgery, neither a pituitary adenoma nor eosinophilic hyperplasia was present. It is likely that this patient's acromegaly resulted from the presence of chronically high normal levels of growth hormone.