What is progesterone?

Progesterone is a sex hormone, playing a role in reproduction and in the development of sexual characteristics during puberty. It is synthesised in both men and women, from cholesterol under the action of the luteinising hormone (LH). Progesterone can then be converted into androstenedione, then into testosterone or estradiol. This hormone belongs, just like theestrogen, to the large family of steroid hormones.

In women, progesterone is a hormone primarily secreted by the ovarian corpus luteum, which plays a role during the third phase of the menstrual cycle , also known as the luteal phase, and during pregnancy. The level of progesterone significantly increases during this phase, before gradually decreasing and returning to a low level at the start of the next cycle.

Progesterone is also present in men, found in the testicles and adrenal glands, but in very small quantities. It notably influences spermatogenesis and the synthesis of testosterone in Leydig cells. Progesterone can also modulate the synthesis of gonadotropin, a hormone that stimulates the activity of the gonads.

The synthesis of progesterone experiences a significant increase during the luteal phase of the menstrual cycle, which is after ovulation. The ruptured follicle containing the egg transforms into the corpus luteum and begins to produce this hormone. Progesterone prepares the body for a potential pregnancy by strengthening the uterine lining (or endometrium), which aids in the implantation of the fertilised egg. When the egg is fertilised, progesterone helps to maintain the pregnancy and reduces the risk of miscarriage. It also works in synergy with oestrogens to stimulate the development of mammary glands in preparation for lactation.

The increase in progesterone synthesis during the third phase of the menstrual cycle is also correlated with the onset of the premenstrual syndrome (PMS), typically characterised by breast tenderness, irritability and acne. Some studies suggest that progesterone may have an effect on the serotonin, gamma-aminobutyric acid and dopamine systems, neurotransmitters involved in mood regulation. Progesterone can also interact with the renin-angiotensin-aldosterone system (RAAS), which could explain the bloating and swelling that occur during the luteal phase.

The effects of progesterone on the skin are less well understood than those of oestrogens. However, an increase in sebum production is often correlated with the heightened synthesis of progesterone observed during the second half of the menstrual cycle. This is one of the reasons why the skin appears oilier and is more prone to blemishes and the onset of hormonal acne during this phase. The pores are also more visible. It appears that progesterone acts by binding to a receptor in the sebaceous glands.

Following menopause, when the synthesis of progesterone ceases, the skin often becomes drier and less hydrated, due to the deterioration of the hydrolipidic film. Predominantly composed of water and sebum, this film deteriorates when the secretion of sebum by the sebaceous glands decreases. The skin then becomes more vulnerable to external aggressions (wind, cold, pollution...).

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• SKOUBY S. & al. Menstrual cycle and skin reactivity. Journal of the American Academy of Dermatology (1991).

• HALBREICH U. The aetiology, biology, and evolving pathology of premenstrual syndromes. Psychoneuroendocrinology (2003).

• TARABORRELLI S. Physiology, production and action of progesterone. Acta Obstetricia et Gynecologica Scandinavia (2015).

• MILLINGTON G. & al. The menstrual cycle and the skin. Clinical and Experimental Dermatology (2015).