Acromegaly associated with a granular cell tumor of the neurohypophysis: aclinical and histological study - Case report

Acromegaly is usually caused by a growth hormone (GH)-secreting pituitary a denoma, and hypersecretion of GH-releasing hormone (GHRH) from a hypothalam ic or neuroendocrine tumor accounts for other cases, The authors report on the unusual association of acromegaly with a granular cell tumor of the neu rohypophysis. A 42-year-old woman with a 10-year history of acral enlargement, headache, and menstrual abnormalities was referred to our department for a suspected GH-secreting pituitary adenoma; The patient's basal GH levels were mildly e levated at 4.8 mu g/L, were not suppressed in response to an oral glucose t olerance test, and increased paradoxically after administration of thyrotro pin-releasing hormone. The patient's insulin-like growth factor-1 (IGF-1) l evel was elevated at 462 mu g/L, whereas a magnetic resonance image of the sella turcica revealed an intra- and suprasellar lesion that was compatible with a diagnosis of pituitary adenoma. A transsphenoidal approach to remov e the lesion, which was mainly suprasellar, was successful during a second operative attempt, resulting in the clinical and biochemical regression of the patient's acromegaly. Four months postoperatively, the patient's basal GH level was 0.9 mu g/L and her IGF-1 level was 140 mu g/L. Histological an alysis of the operative specimen demonstrated a granular cell tumor of the neurohypophysis, which when stained proved negative for pituitary hormones and GHRH. This case represents the first reported association between a granular cell tumor of the neurohypophysis and acromegaly. Granular cell tumor of the ne urohypophysis could be added to the restricted list of neoplastic causes of acromegaly secondary to hypersecretion of a GH-releasing substance.