Endocrine Abstracts

The classic view of sexual differentiation in mammalian species holds that sex differences in the brain and behavior develop under the influence of estrogens derived from the neural aromatization of testosterone: the brain develops as male in the presence of estrogens and as female in their absence. In agreement with this view, it has been proposed that the female brain needs to be protected from estrogens produced by the placenta and that alpha-fetoprotein (AFP) - a major fet...

Androgens and estrogens are transported bound to the sex hormone binding globulin (SHBG). SHBG is believed to keep sex steroids inactive and to control the amount of free hormones that enter cells by passive diffusion. Contrary to the free hormone hypothesis, we demonstrate that megalin, an endocytic receptor in reproductive tissues acts as a pathway for cellular uptake of biologically active androgens and estrogens bound to SHBG. In line with this function, lack of receptor e...

The main product of the thyroid is thyroxine (T4). However, the physiological ligand of nuclear thyroid hormone receptors is triiodothyronine, T3. Deiodination of T4 to yield T3 is achieved by 5′-deiodinase activity. Type I-deiodinase (Dio1) was the first deiodinase cloned and its strong expression in liver and kidny, together with the size of these organs, suggested a role for Dio1 in peripheral conversion of T4 to T3. Later, Dio2 and Dio3 were cloned, enzymes with a mo...

The discovery that IGF binding proteins (IGFBPs) are capable of action independently of ligand binding opened up a broad scope of investigation into the mechanisms by which the IGFBPs elicit their intrinsic cellular effects. Numerous studies have demonstrated the special role of IGFBPs in as diverse processes as cell proliferation, migration and survival/apoptosis. However, the pathways by which these actions occur have not been completely defined but interactions of IGFBPs wi...