Conclusions and Relevance This systematic review and meta- analysis did not show a significant beneficial or detrimental association of HT with muscle mass .
Importance Hormone therapy ( HT ) has been suggested for protection against age-related muscle weakness in women .
However , the potential for HT-associated health risks necessitates a better underst and ing of the direction and magnitude of the association between HT and health outcomes , such as lean body mass ( LBM ) .
Objective To determine whether HT was associated with reduced LBM loss compared with not receiving HT  among postmenopausal women aged 50 years and older .
Estrogen/gestagen therapy changes soft tissue body composition in postmenopausal women.
The long-term effect of percutaneous and oral estrogen replacement therapy on soft tissue body composition was examined in a two-year , placebo-controlled study with 110 early postmenopausal women . The women were allocated to four treatment groups : ( 1 ) oral cyclical combination of estradiol valerate and cyproterone acetate , ( 2 ) oral placebo , ( 3 ) percutaneous 17 beta-estradiol , supplemented by oral progesterone during the second year , or ( 4 ) percutaneous placebo cream .  Total-body lean body mass ( LBM ) and fat mass ( FM ) were measured by dual photon ( 153Gd ) absorptiometry once a year , and the fat layer in the distal forearm ( FATarm ) was measured every 3 months by single photon ( 125I ) absorptiometry . Both hormone therapies prevented an increase in FATarm , as observed in the placebo groups . A similar pattern was seen for FM , body weight , and skin-fold thickness ( measured once a year by mechanical calipers ) , whereas LBM was unaffected by the therapy . Hormonal replacement therapy prevents the age-related increase in body fat observed after the menopause
Conclusions and Relevance This systematic review and meta- analysis did not show a significant beneficial or detrimental association of HT with muscle mass .
Importance Hormone therapy ( HT ) has been suggested for protection against age-related muscle weakness in women .
However , the potential for HT-associated health risks necessitates a better underst and ing of the direction and magnitude of the association between HT and health outcomes , such as lean body mass ( LBM ) .
Objective To determine whether HT was associated with reduced LBM loss compared with not receiving HT  among postmenopausal women aged 50 years and older .