High prevalence rate of pituitary incidentaloma: is it associated with the age-related decline of the sex hormones levels?

Incidental pituitary adenoma is the common finding during brain imaging. According to multistep model of pituitary tumourigenesis genetic alterations provide the initiating event that transforms cells while hormones play a role in promoting cell proliferation. Development of pituitary adenoma in a case of excessive hypophysiotrophic hormones production or reduced feedback suppression by target gland hormones emphasizes the importance of hormonal stimulation in pituitary tumourigenesis. Pituitary hyperplasia has been reported in pregnancy, hypothyroidism and conditions such as CRH or GHRH hypersecretion. Moreover, recent study reported one case of gonadotroph macroadenoma and two cases of gonadotroph cells hyperplasia in patients with Klinefelter syndrome probably due to protracted stimulation of gonadotroph cells because of lack of androgen feedback. Significant changes of the hypothalamic-pituitary-gonadal axis occurred with aging. In females, after menopause, estradiol level decreases by 35-fold and estrone level by 20-fold that results in increased gonadotropins levels. Similarly, FSH, but not LH, level is increased with advancing age in men, too, although the age-related difference in the level is less in comparison with women. Regarding these data, we hypothesised that high prevalence rate of pituitary incidentaloma in the elderly is associated with age-related decline in sex hormones levels and subsequent lack of feedback suppression leading to permanent gonadotrophs stimulation which is the crucial step in the pituitary tumour development. According to previously mentioned multistep model of pituitary tumourigenesis, incidentaloma will develop only in persons with already present intrinsic pituitary cell defects. However, further studies have to answer the questions of whether the incidence of pituitary tumours is more frequent in elderly, whether women with late onset menopause or those taking long-term hormone replacement therapy have lower rate of pituitary incidentaloma, and finally, is there any correlation between pituitary tumours incidence and serum concentrations of LH, FSH, bioavailable testosterone or estradiol.