is an important estrogen steroid hormone in both women and men. It is a typical steroid with core four-ring system (ABCD), composed of 17 carbon atoms. Cutting Ring B produces secosteroids one of which is vitamin D3. (5ien). Calcitriol is the active form of vitamin D pro-hormone.

• Steroid Hormones and their receptors

Types by function

Corticosteroids

Glucocorticoids

Cortisol, a glucocorticoid whose functions include immunosuppression Mineralocorticoids: Aldosterone, a mineralocorticoid which helps regulate blood pressure through water and electrolyte balance Sex steroids:

Progestogens

Progesterone, which regulates cyclical changes in the endometrium of the uterus and maintains a pregnancy

Androgens

Testosterone, which contributes to the development and maintenance of male secondary sex characteristics

Estrogens

Estradiol, which contributes to the development and maintenance of female secondary sex characteristics

Additional classes of steroids include

Neurosteroids such as DHEA and allopregnanolone Aminosteroid neuromuscular blocking agents such as pancuronium bromide

As well as the following class of secosteroids (open-ring steroids)

Vitamin D forms such as ergocalciferol, cholecalciferol, and calcitriol