Progesterone treatment is given as part of hormone replacement therapy (HRT) for women with a uterus. This is because the oestrogen component of HRT causes the womb lining (endometrium) to thicken, and progesterone causes it to shed. Without progesterone, the thickened endometrium would result in an increased cancer risk.
Micronized progesterone is body-identical
Current regulated HRT preparations contain progesterone in one of two forms: synthetic (progestogens or progestins) or ‘body identical’. The former includes levonorgestrel and norethisterone. Because synthetic progestogens are not identical in structure to the progesterone made by the human body, they are associated with more side effects.
On the other hand, the latter is chemically and structurally identical to the progesterone produced in the human body and has fewer side effects. The body-identical type of progesterone is available is called ‘micronised (or micronized) progesterone’.
The brand names of micronized progesterone
In the UK, micronized progesterone is marketed as Utrogestan®. In the US and Australia, it is available as Prometrium®.
What does micronise mean?
Micronization is a pharmaceutical process by which a substance is produced that has tiny particles of a similar size – less than 10 microns, or 10-6 m – and up to ten times smaller than a standard drug particle. Their tiny size enhances solubility and promotes steady and even absorption, increasing bioavailability – the ability of the substance to be used readily by the body.
What is micronized progesterone made from?
Micronized progesterone is derived from plants, usually wild yams (a root vegetable). The relevant chemicals contained in the plants are extracted and pharmaceutically converted into the required hormone preparation. Unlike synthetic progestogens, the result is identical to the progesterone produced in the body.
Methods of taking micronised progesterone
There are different regimens – cyclical or continuous – of taking micronised progesterone in Utrogestan® and Prometrium®, depending on if you are perimenopausal or postmenopausal. The administration route is typically oral, but in some cases, vaginal may be preferred. The four regimens are described below, but verifying the best regimen for yourself with your doctor is important.
Cyclically
For women still having periods within the last year, the usual dose is 2×100 mg capsules taken for 12 consecutive days, on days 15 to 26 of the natural cycle. Day 1 then repeats every 28 days. So, if you start a course of micronised progesterone on a Friday night, the subsequent course will commence exactly four weeks later, or in 4 Friday’s time. This creates an artificial 28-day cycle and monthly bleed.
Continuously
For postmenopausal women who have not had a natural period in more than one year, the usual dose is 1×100 mg capsule every day, either on days 1 to 25 or continuously without stopping.
Orally
Most prescriptions will come with the advice to take micronised progesterone orally. Taking it with food can increase the sedative effect, so taking it on an empty stomach is better.
Vaginally
For women who experience side effects such as mood swings and anxiety from taking micronised progesterone orally, the vaginal administration route can be considered. The capsule is placed into the vagina at night-time and is absorbed from the back of the vagina into the uterus. The absorption works so well that you may be advised to take it only every alternate day; check with your healthcare provider. In the UK, NICE does not authorize Utrogestan® as a vaginal suppository, and advice from a private menopause specialist may be required.
Side effects
Side effects of taking micronized progesterone are similar to those women often get before their period: bloating, breast tenderness, mood swings, and spot breakouts. Mood swings – while occurring less than with synthetic progestogens – are reported in approximately ten percent of women. In these cases, it can be worth discussing with your doctor the option of taking the capsules vaginally, as mentioned above.
Intermittent or continual vaginal bleeding can occur, and if this worsens or lasts for longer than six months, you should seek advice from a medical professional.
Micronized progesterone often causes mild drowsiness, so it is necessary to avoid taking it before operating machinery or driving. Before bed is the preferable time for administration. While this sedative effect can improve sleep quality, it does not usually extend into the following day.
Safety
Better than synthetic progestogens
Micronized progesterone does not increase the risks of blood clots and heart disease, unlike the elevated risk associated with synthetic progestogens. It does not attenuate the cardiovascular benefits of oestrogen, unlike synthetic progestogens. Within the first five years of taking micronised progesterone, there is no increased risk of breast cancer. Beyond that, the risk is very low and significantly lower than when taking synthetic progestogens.
Therefore, body-identical micronised progesterone is considered the safest form of progesterone for HRT treatment. Along with transdermal oestrogen, it is currently considered one of the optimal HRT regimens.
Allergies
Amongst the non-medicinal ingredients in Prometrium® are soya lecithin and peanut oil, so consumption by sufferers of peanut or soya allergies should be avoided. Utrogestan® also contains soybean lecithin, and due to the possible relationship between allergies to soya and peanuts, it should be avoided by patients with either of these conditions.
Always check with your doctor before starting a new medicine
Always check the ingredient list fully to ensure the treatment suits you, and check with a doctor before starting a new treatment regime.
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