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

Abstract

Objective: Nonfunctioning pituitary adenomas (NFPA), which represent about one-quarter of human pituitary tumors, occur in middle or old age. Determination 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, is important to distinguishing hypogonadal status due to the normal decline of gonadal function from that due to hypothlalamic-pituitary dysfunction. The aim of the study was to verify whether this difference still persists in old subjects, despite the physiological decline of gonadotropins in the last decades of life. Design and methods:The study included 154 healthy subjects (aged 50-104 years) and 47 patients with NFPA (aged 50-80 years). Blood samples were collected after an overnight fast and hormone levels were measured by two immunofluorimetric assays. Results: In healthy women the highest serum levels of gonadotropins were present in the 50-60 year age group, with a slight but progressive age-associated decrease in serum FSH and LH being observed thereafter. In healthy men serum gonadotropin levels were stable up to 70 years, increased up to 75-85 years and thereafter gradually decreasing. Female patients with NFPA showed 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 subjects. A high sensitivity and specificity of gonadotropin measurements (about 90%) for the diagnosis of NFPA was observed in female patients aged 50-80 years. In male subjects, a large overlap of gonadotropin values in NFPA and controls, namely over the 50-70 years age range, was observed. Conclusions: Our study demonstrates that despite the gradual decline of gonadotropin levels in healthy postmenopsausal women, the reduction of both FSH and LH persists in old patients with NFPA, suggesting that measurement of gonadotropin levels could prove useful in the evaluation of pituitary lesions even in old women. More subtle differences seem to occur in male subjects.

Male hypogonadism. Part I: Epidemiology of hypogonadism

“…32 Others use a threshold of o200 ng/dl to trigger magnetic resonance imaging (MRI). 33,34 Some authorities recommend sellar MRI with thyroxine, cortisol, and prolactin assessments when secondary hypogonadism is considered likely. 33 Based on extensive hormonal evaluation of elderly men with normal and low levels of T, as compared with those with primary and secondary hypogonadism and young, healthy volunteers, a Swiss group 28 recently developed an algorithm for the use of GnRH testing to discriminate secondary, hypogonadotropic hypogonadism from PADAM.…”

Changes in Estrogen Receptor-α and -β in the Infundibular Nucleus of the Human Hypothalamus Are Related to the Occurrence of Alzheimer’s Disease Neuropathology

“…Although these levels remain higher than that recorded in younger population, a declined gonadotropin serum levels is observed with age in elderly subjects. In women, although not in all studies (22), a decline in both FSH and LH levels occurs with age after menopause (19,23), and decreased gonadotropins secretion with age is also observed in aged men (24). This indicates that gonadotropin secretion is influenced by not only sex steroid and peptide feedback but also by age.…”

FSH secretion predominates in vivo and in vitro in patients with non-functioning pituitary adenomas

“…In contrast to the predicted gonadotrophin hypersecretion, a more frequent finding in patients with NFPAs are low levels of LH and FSH compared with an age-matched healthy population. A recent study of serum gonadotrophin levels in 47 patients (aged 50 -80 years) with NFPAs (8) reported that female patients showed levels of gonadotrophins which were far lower than those observed in agematched healthy women. In male patients, serum FSH levels were similar to those in age-matched controls, although patients did show a significant reduction in LH when compared with healthy men, again supporting a decrease in the LH:FSH ratio.…”

“…However, a recent study comparing gonadotrophin levels in healthy subjects with NFPA patients, all aged . 50 years, showed levels of gonadotrophins in female patients which were far lower than controls, and in male patients a large overlap of gonadotrophin values with controls was observed (8). This is most likely due to the late stage of presentation of these patients such that the tumour mass compresses the normal pituitary, thereby impairing hormone production.…”