Gonadotroph Cell Adenomas of the Pituitary*

Abstract

Although the frequency of gonadotroph cell adenomas among all unselected pituitary adenomas is not yet known, it is probably much higher than previously suspected. The true incidence is probably somewhere between the 3-4% found in surgical and autopsy series, which is probably an underestimate because of its reliance on tissue content, and the 17% (24% when alpha-secreting adenomas are included) of 139 patients from this institution, which may be an overestimate of the incidence among all adenomas, because it is heavily weighted to very large adenomas in men only. Most patients who have been reported to have gonadotroph cell adenomas have similar clinical characteristics. Most are middle-aged men who have a history of normal pubertal development and a normal fertility history, and by examination are normally virilized and have testes of normal size. They are brought to medical attention because of visual impairment, which is the result of the enormous size of the adenoma. The most common hormonal characteristic of gonadotroph cell adenomas in vivo is hypersecretion of FSH, which is often accompanied by hypersecretion of FSH beta and alpha-subunit and less often by hypersecretion of LH beta or intact LH. Another common characteristic is secretion of FSH and/or LH in response to TRH. A few patients with gonadotroph cell adenomas hypersecrete intact LH and, therefore, have supranormal serum testosterone concentrations. A larger number have secondary hypogonadism because the adenomas are not secreting intact LH, but are compressing the normal gonadotroph cells and impairing LH secretion. These patients have concentrations of intact LH that are not elevated in spite of subnormal testosterone concentrations. Testosterone levels increase markedly in response to hCG. The hormonal characteristics of gonadotroph adenomas in dispersed cell culture are similar to their characteristics in vivo, including hypersecretion of FSH and LH subunits and responsiveness to TRH. Both the clinical and hormonal characteristics of gonadotroph cell adenomas usually make them readily distinguishable from pituitary enlargement due to long-standing primary hypogonadism. Pituitary adenomas that hypersecrete only alpha-subunit in vivo may also be adenomas of gonadotroph cells, because some of them secrete large amounts of FSH as well as alpha-subunit in culture. Most gonadotroph cell adenomas are now treated first by transsphenoidal surgery, to attempt to restore vision as quickly as possible, and then by supervoltage radiation to prevent regrowth of the remaining adenomatous tissue.(ABSTRACT TRUNCATED AT 400 WORDS)