GROWTH HORMONE-RELEASING HORMONE AND SOMATOSTATIN IN NORMAL AND TUMORAL HUMAN PITUITARIES

In order to further understand the role of endogenous pituitary neuropeptides in pituitary hormonal content and secretion, GHRH, SRIH and GH contents were quantified in GH adenomas obtained from acromegalic patients with plasma GH levels either high (> 5-mu-g/l, range 11 to 550-mu-g/l, n = 11) or in the normal range (< 5-mu-g/l, range 1 to 3.3-mu-g/l, n=4). Values were compared to those found in normal human pituitaries. No relationship was found between GHRH content and plasma GH or between SRIH and GH content when considering together adenomas and normal pituitaries. Results showed that there is a positive relationship between GHRH and GH content: when GHRH content is high, GH content is also high (normal pituitaries and GH adenomas of acromegalic patients with high plasma GH) and when GHRH content is low, GH content is also low (GH adenomas of acromegalic patients with plasma GH in the normal range). Conversely, SRIH content is negatively related to plasma GH levels: when SRIH is present, plasma GH is in the normal range; when SRIH is undetectable, plasma GH is high.