Progesterone

What is progesterone?

Progesterone is a steroid hormone that plays an important role in female reproduction (R). Its effects are mediated via progesterone receptors that are distributed in tissues around the body (R).

Among women of reproductive age, the level of progesterone fluctuates throughout the menstrual cycle, peaking at about a week after ovulation. This coincides with the exacerbation of certain skin conditions including acne, eczema and dermatitis (R). Menopause leads to a relatively rapid fall in the level of progesterone (R).

In men, progesterone influences the synthesis of testosterone and the production of sperm. However, serum progesterone concentrations do not change with age in men (R).

Is progesterone stable?

A formulation containing 1% progesterone in liposomes was found to have very poor chemical stability, with 61% of the progesterone degraded after only 2 weeks of storage at room temperature. Microbial contamination was also observed. When the liposomes were coated with various polymers, both the chemical and the microbial stability of the formulation were improved. Polycarbophil, chitosan-EDTA and the polymeric emulsifier were the best polymers, leading to virtually all of the progesterone being preserved even after 2 months of storage (R).

Similarly, progesterone formulated in a microemulsion was degraded by 45% after 6 months of storage at room temperature, but when a polymeric emulsifier was added, 64% of the progesterone remained after 6 months, and when silicon dioxide was added, 70% of the progesterone remained after 6 months (R).

Formulations containing 20% progesterone in addition to 1% estradiol, 2% estriol, 1% estrone and 5% testosterone have been demonstrated to remain stable when incorporated in 3 different cream bases and refrigerated or stored at room temperature for 6 months (R).

Does progesterone get absorbed?

Progesterone in cream form can be absorbed through the skin, but there is conflicting evidence on whether it significantly raises serum levels of progesterone (R, R). Progesterone from creams has been shown to be retained in the skin for a relatively long period (R), perhaps because it saturates the fatty layer below the dermis (R).

Progesterone gels on the other hand appear to enter the skin's microcirculation rapidly, because they are taken up and released by the red blood cells passing through the capillaries, resulting in elevated serum progesterone levels (R).

Penetration enhancers can be used to increase the permeation of progesterone through the skin (R, R).

What happens after progesterone is absorbed?

Progesterone may bind to progesterone receptors expressed in keratinocytes, fibroblasts, sebaceous glands and hair follicles in the skin (R, R, R). It is also metabolised by human fibroblasts (R, R).