ABSTRACT
Males are typically larger, with enhanced muscular development related to copulatory postural requirements and aggressive social mannerisms coincident with mating behavior. Testosterone, following conversion to estrogen, causes the epiphyses to fuse to the long bones, and halts linear body growth. Male sex steroids promote hair pigmentation and growth in mammals, and feather pigmentation and growth in birds. Hair fibers are coarser than those of females, and hair coat is usually darker. Testosterone also stimulates erythropoiesis, increases the BMR, and maintains, with FSH, spermatogenesis.
