Effect of aging on serum gonadotropin levels in healthy subjects and patients with nonfunctioning pituitary adenomas

Objective: Nonfunctioning pituitary adenomas (NFPA), which represent about one-quarter of human pituitary tumors, occur in middle or old age. Determin ation of gonadotropin levels, which are not expected to be high during the early postmenopause in normal women and which are low in women with NFPA, i s important to distinguishing hypogonadal status due to the normal decline of gonadal function from that due to hypothlalamic-pituitary dysfunction. T he aim of the study was to verify whether this difference still persists in old subjects, despite the physiological decline of gonadotropins in the la st decades of life. Design and methods: The study included 154 healthy subjects (aged 50-104 ye ars) and 47 patients with NFPA (aged 50-80 years). Blood samples were colle cted after an overnight fast and hormone levels were measured by two immuno fluorimetric assays. Results: In healthy women the highest serum levels of gonadotropins were pr esent in the 50-60 year age group, with a slight but progressive age-associ ated decrease in serum FSH and LH being observed thereafter. In healthy men serum gonadotropin levels were stable up to 70 years, increased up to 75-8 5 years and thereafter gradually decreasing. Female patients with NFPA. sho wed levels of gonadotropins which were far lower than controls. Only three patients had levels of both FSH and LH above the 2.5 centile for normal sub jects. A high sensitivity and specificity of gonadotropin measurements (abo ut 90%) for the diagnosis of NFPA was observed in female patients aged 50-8 0 years. In male subjects, a large overlap of gonadotropin values in NFPA a nd controls, namely over the 50-70 years age range, was observed. Conclusions: Our study demonstrates that despite the gradual decline of gon adotropin levels in healthy postmenopsausal women, the reduction of both FS H and LH persists in old patients with NFPA, suggesting that measurement of gonadotropin levels could prove useful in the evaluation of pituitary lesi ons even in old women, More subtle differences seem to occur in male subjec ts.