Acromegaly and thymic hyperplasia: a case report.

Growth hormone overproduction is characterized by increased size of visceral organs as well as growth of bone and soft tissues. We describe a case of a 23-year-old female acromegalic patient, who had been previously unsuccessfully operated upon by transsphenoidal pituitary surgery and then irradiated. In November 1987 a routine X-ray chest examination revealed a mediastinal mass, subsequently confirmed by CT scan. The patient underwent surgical removal of the mass: macroscopical aspect, histological sections and immunocytochemistry showed typical thymic structures without any evidence of neurosecretory activity. No GH-positive cells were found and only small amounts of immunoreactive GHRH like material (9.2 ng/g wet wg) were detected in the tumor extract. Before surgery plasma GHRH levels were not elevated (26 pg/ml); serum GH and IGF-I levels were 27.4 +/- 4.9 micrograms/l and 191 nmol/l, respectively, and remained unchanged after surgery. These data ruled out a GHRH and/or GH ectopic production, confirming the primitive pituitary origin of acromegaly in this patient. It is likely that thymic hyperplasia may be explained by longstanding overproduction of GH and the young age of the patient.