Glycoprotein hormone α subunit secretion by pituitary adenomas: influence of external irradiation

In ninety-nine patients with pituitary adenomas, forty-six with acromegaly, the serum level of the glycoprotein hormone α subunit was elevated in eighteen cases. Thirteen of these were acromegalic and one had an FSH-producing tumour. Alpha levels varied little during the day, from one day to the next and over a 6 month period. In twenty-five patients with a variety of other hypothalamic-pituitary disorders examined, one patient with a craniopharyngioma had a mildly elevated α level. External pituitary irradiation was followed by an acute and often transient fall in α level in several of these patients. Of the fifty-four patients with pituitary adenomas who had received external irradiation before testing, only five had elevated α subunit levels compared with thirteen patients of the forty-five who had not been irradiated. This difference in incidence of elevated α level was statistically significant (P<0.025). It is concluded that external irradiation may reduce α subunit level chronically in many patients with pituitary adenoma. (author)