SHBG (sex hormone binding globulin) binds to testosterone and estradiol. High SHBG may decrease free testosterone and free estradiol.

 Progesterone is a female hormone important for the regulation of ovulation and menstruation. It is also present in men in smaller concentrations. Progesterone is a steroid hormone that plays numerous roles within the human body. It is crucial to the production of sex hormones and corticosteroids, as well as playing a role as a neuro-steroid (brain function).