Nutrition Guide

In many contexts, the two main classes of sex steroids are androgens and estrogens, of which the most important human derivatives are testosterone and estradiol, respectively. Other contexts will include progestagen as a third class of sex steroids, distinct from androgens and estrogens. Progesterone is the most important and only naturally-occurring human progestagen. In general, androgens are considered “male sex hormones”, since they have masculinizing effects, while estrogens and progestagens are considered “female sex hormones”[1] although all types are present in each gender, albeit at different levels.

Sex steroids include:
androgens:
testosterone
androstenedione
dihydrotestosterone
dehydroepiandrosterone
anabolic steroids
estrogens:
estradiol
estrone
progestagens:
progesterone
progestins

There are also many synthetic sex steroids. Synthetic androgens are often referred to as anabolic steroids. Synthetic estrogens and progestins are used in methods of hormonal contraception. Ethinylestradiol is a semi-synthetic estrogen.

Sex steroids play important roles in inducing the body changes known as primary sex characteristics and secondary sex characteristics.

The development of both primary and secondary sexual characteristics is controlled by sex hormones after the initial fetal stage where the presence or absence of the Y-chromosome and/or the SRY gene determine development.

Natural sex steroids are made by the gonads (ovaries or testes), by adrenal glands, or by conversion from other sex steroids in other tissue such as liver or fat.

Sex steroids, also known as gonadal steroids, are steroid hormones that interact with vertebrate androgen or estrogen receptors. Their effects are mediated by slow genomic mechanisms through nuclear receptors as well as by fast nongenomic mechanisms through membrane-associated receptors and signaling cascades. The term sex hormone is nearly always synonymous with sex steroid.

In a normal menstrual cycle, a sudden drop in progesterone levels triggers menstruation. Norethindrone acetate (brand name Aygestin) and medroxyprogesterone acetate (brand name Provera) may be used to artificially induce progestogen withdrawal bleeding

Progestinic compounds decrease luteinizing hormone (LH) levels[1] and as such, will have antiandrogenic properties in trans-women and cisgender males alike, due to decreased LH stimulation of the testes. Cyproterone is a common example of a progestinic medication, and is an effective antiandrogen, which has the added benefit of blocking androgen receptors in addition to the progestinic feedback to decrease LH levels.

Progestogens are used alone in progestogen only pills, or with an estrogen in combined oral contraceptive pills, a contraceptive patch, and a contraceptive vaginal ring.
Medroxyprogesterone acetate (Depo-Provera) and norethindrone enantate (Noristerat) are used by depot injection.
Etonogestrol is released by subcutaneous implants (Implanon). Norplant and Jadelle implants release levonorgestrel.
Levonorgestrel is released by the intrauterine system IUS (Mirena).

The role of the placenta in progestagen production varies by species. In the sheep, horse, and human, the placenta takes over the majority of progestagen production, whereas in other species the corpus luteum remains the primary source of progestagen. In the sheep and human, P4 is the major placental progestagen.

The equine placenta produces a variety of progestagens, primarily 5?DHP and 20?5P, beginning on day 60. A complete luteo-placental shift occurs by day 120-150.

Progesterone (P4) is the major progestagen produced by the corpus luteum in all mammalian species. Luteal cells possess the necessary enzymes to convert cholesterol to pregnenolone (P5), which is subsequently converted into P4. P4 is highest in the diestrus phase of the estrous cycle.