The maintenance of pregnancy is dependent on numerous endocrinological events that eventually lead to the successful growth and development of the fetus. Although the great majority of pregnant women have no preexisting endocrine abnormalities, a small number of women can have endocrine alterations that could potentially lead to recurrent pregnancy losses. It is estimated that approximately 8 to 12% of all pregnancy losses are the result of endocrine factors. Progesterone is essential for successful implantation and maintenance of pregnancy. Therefore, disorders related to inadequate progesterone secretion by the corpus luteum may affect the outcome of the pregnancy. Luteal phase deficiency, hyperprolactinemia, and polycystic ovarian syndrome are some examples of endocrine disorders affecting pregnancy. Several other endocrinological abnormalities such as thyroid disease, hypoparathyroidism, uncontrolled diabetes, and decreased ovarian reserve have been implicated as etiologic factors for recurrent pregnancy loss. Inhibins and activins are nonsteroidal glycoproteins thought to have important roles in reproductive physiology and are proposed as markers of fetal viability.