Basal serum concentrations of glycoprotein hormone α-subunit and its response to GH-releasing hormone (GHRH) were studied in 22 acromegalic patients and in normal subjects. Four out of 22 patients had a basal α-subunit concentration (1.2-3.5 ng/ml) clearly above the upper limit of the normal range. GHRH injection (1 μg/kg body weight, bolus dose iv) produced a clear α-subunit response [mean % increase: 120 ± 37 (SD)] in the 4 patients with elevated basal α-subunit levels. No increase in serum glycoprotein hormones (TSH, LH, and FSH) occurred. Selective adenomectomy in 2 patients resulted in normalization of both serum GH and α-subunit levels, as well as disappearance of the abnormal α-subunit response to GHRH. In in vitro studies, only these 2 adenomas secreted α-subnit in large amounts (534 and 388 ng/mg protein·30 min) and was it further stimulated by GHRH (% increase: 83 and 126). Morphological studies done with protein A-gold particle immunotechnique demonstrated that in these adenomas the great majority of the cells contained secretory granules positive for both GH and α-subunit. We conclude that: 1) α-subunit hypersecretion is present in some acromegalic patients (about 20%), 2) GHRH stimulates α-subunit release both in vivo and in vitro only in patients with elevated basal α-subunit levels, and 3) in these patients α-subunit derives from a common adenomatous cell secreting both α-subunit and GH molecules.
|Number of pages||6|
|Journal||Journal of Clinical Endocrinology and Metabolism|
|Publication status||Published - 1985|
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism