Man labioscrotal folds into the scrotum. Another significant hormone in sexual differentiation is the anti-Müllerian hormone, which inhibits development of the Müllerian ducts. In general, men suffer from many of the same illnesses as women. In comparison to women, men suffer from slightly more illnesses. Male life expectancy is slightly lower than female life expectancy, although the difference has narrowed in recent years. For males during puberty, testosterone, along with gonadotropins released by the pituitary gland, stimulates spermatogenesis, along with the full sexual distinction of a human male from a human female, while women are acted upon by estrogens and progesterone
Fraternal birth order and male sexual orientation fraternal birth order (or the underlying variable it reflects) may be the first universal factor to be identified in development of same-sex attraction in males. Bearman and Brückner (2002) argued that studies showing a fraternal birth order effect have used nonrepresentative samples and/or indirect reports on siblings' sexual orientation. Their analysis, focusing on opposite-sex twins, did not find an association "between same-sex attraction and number of older siblings, older brothers, or older sisters". A study by Francis (2008), using the same Add Health survey but with broader analysis, saw a very weak correlation of male same-sex attraction with having multiple