Plasma growth hormone half-life after selective removal of adenoma in acromegalics determines the outcome of surgery.

Abstract

We measured plasma GH levels during transsphenoidal surgery in eight patients with acromegaly. After removal of the adenoma GH levels fell monoexponentially in six subjects while they were still under general anaesthesia, but no decrease was noted for two other subjects. Normal postoperative GH and Somatomedin-C levels were found for those patients who exhibited a reduction in GH during surgery. During follow-up studies one patient with a normal GH level exhibited a paradoxical reaction to TRH, attributed to tumour remnants. The plasma half-life found for five patients was 18-33 min; for another cured subject it was longer, i.e. 58 min. The major fraction of the circulating GH, as determined by gel-chromatography, was mol. wt 22,000; this applied for six subjects, while the patient with the long plasma half-life appeared to have a mol. wt 33,000 variant. From this study we conclude that a clear drop in the plasma GH level after removal of the adenoma predicts a favourable outcome of surgery; however, if some tumour remnants are left behind, paradoxical reactions may occur despite normal basal GH levels.