| Popis: |
Androgen actions in target tissues depend on plasma concentration of bio-available androgen, on local androgen metabolism and on the presence and activity of sex steroids receptors (AR and partially ER) in association with regulatory co-factors, as well as on non-genomic pathways. As evidenced by androgen receptor insensitivity syndromes, androgens appear to play an important role in the development of the male skeletal phenotype, especially bone size. It is also probable that androgens participate in the later maintenance of adult bone remodelling/mass/structure. The old concept that androgens are responsible for skeletal abnormalities in hypogonadism is only partially erroneous. The declining sex steroid levels in the elderly may adversely affect the preservation of skeletal integrity and indicates that aromatisation of testosterone to estradiol is an important mediator of bone metabolism in the elderly. Androgens and estrogens have actions in bone development and maintenance and the complex interplay between both has only partially elucidated. |
