Progesterone

What is Progesterone?

Alongside oestrogen, progesterone is one of the primary female sex hormones that supports the menstrual cycle and pregnancy. It is sometimes called the pregnancy hormone.

Where is progesterone produced?

Progesterone belongs to a class of steroid hormones called progestogens. It is produced by the adrenal cortex, reproductive glands and the brain in both men and women^[1].

Following ovulation, the release of an egg from the ovary, progesterone is produced by the corpus luteum, a temporary group of cells that are critical during the luteal phase of the menstrual cycle^[2].

The Role of Progesterone In Women

Progesterone has several key functions in women’s health:

• Breast development: Progesterone, alongside other hormones, is involved in the development of breasts during puberty and pregnancy^[3].
• Menstrual cycle regulation: Progesterone prepares the body for pregnancy, thickening the lining of the uterus in preparation for the implantation of a fertilised egg. If implantation doesn’t occur, then progesterone levels fall, and a new menstrual cycle begins.
• Pregnancy maintenance: Progesterone is produced by the corpus luteum after ovulation, stimulating an optimal environment for a developing foetus.
• Mood regulation: Progesterone is thought to be protective against depression^[4] and may have a beneficial role in relieving or preventing premenstrual syndrome.

What’s the difference between progesterone and oestrogen?

Progesterone and oestrogen are the primary female sex hormones and are critical for regulating the menstrual cycle, developing sex characteristics in women, and for wider health functions. Although they often work in tandem, oestrogen and progesterone are not the same hormones. Here are the main differences:

	Progesterone	Oestrogen
Production site	Ovaries, specifically the corpus luteum but also the adrenal cortex and brain.	Primarily the ovaries but also the adrenal glands and fat tissues.
Secretion	Secreted by the corpus luteum after ovulation.	Secreted by the ovaries before ovulation.
Functions	Prepares the body for and maintains pregnancy and regulates the menstrual cycle.	Regulates the menstrual cycle and the development of secondary sex characteristics.
Regulation	Regulated by luteinising hormone (LH).	Regulated by follicle-stimulating hormone (FSH).

Progesterone’s Role in Your Menstrual Cycle

One of the main roles of progesterone in women is to prepare the body for pregnancy. So, each month a woman goes through a series of bodily and hormonal changes to prepare for the potential fertilisation of an egg and subsequent pregnancy, as part of the menstrual cycle.

The cycle is split into two phases: follicular and luteal. The first half of the menstrual cycle is called the follicular phase and occurs before ovulation. During this time progesterone levels are quite low because a developing follicle in the ovary stimulates the production of oestrogen. So, oestrogen is the dominant hormone as the body prepares for ovulation.

Once an egg is released, the production of progesterone ramps up in the second half of the cycle, better known as the luteal phase. After an egg is released, the follicle transforms into a ball of cells, called a corpus luteum. The structure secretes progesterone, signalling to the body to thicken the uterine lining and prepare for a potential pregnancy.

If pregnancy occurs, progesterone levels continue to rise and are maintained by the corpus luteum, and then the placenta.

If pregnancy doesn’t happen, progesterone levels fall, and a new cycle begins.

Progesterone’s Role in Perimenopause and Menopause

Progesterone levels fall in the years leading up to menopause when ovulation ceases. This period is called perimenopause and progesterone levels fluctuate widely. Because ovulation can become irregular during this time, progesterone levels can fall, causing changes in menstrual patterns, like irregular, heavier or lighter periods.

Menopause occurs when a woman does not have a period for 12 months in a row. At this time, the ovaries are producing little oestrogen and progesterone, initiating the common menopause side effects, and the cessation of ovulation⁶.

Progesterone’s Role in Fertility

Progesterone’s role following ovulation and preparing the body for pregnancy is directly related to female fertility. Progesterone levels can be assessed to determine if ovulation has occurred which is useful for women who are trying to conceive.

Failing to ovulate is a cause of infertility in around 20% of cases. Low progesterone levels in the luteal phase of the menstrual cycle can indicate ovulation hasn’t occurred or corpus luteum insufficiency^[7].

Low progesterone levels can contribute to irregular periods and make it more difficult for a fertilised egg to grow and develop in the womb.

Progesterone’s Role in Wellbeing

Although progesterone’s primary role is associated with female reproductive health, it also has key benefits for physical and mental wellbeing. For example, it’s associated with:

Mood regulation: Lower levels of progesterone during the luteal phase of the menstrual cycle are a good predictor of the severity of peri-menstrual symptoms^[8].

Sleep quality: At optimum levels, progesterone promotes good sleep, and some research shows that it may help relieve sleep disturbances associated with ageing^[9].

Bone density: Progesterone promotes the formation of new bone and increases bone turnover^[10].

What Causes High Progesterone Levels in Women?

High progesterone levels are not known to cause serious negative health effects. The combined oral contraceptive pill contains progesterone to prevent ovulation and thicken the cervical mucus to prevent pregnancy. Progesterone can also be used as a hormone replacement therapy to relieve the symptoms of menopause.

Progesterone levels may also rise because of the condition, congenital adrenal hyperplasia. Smoking also increases progesterone^[11].

What are the symptoms of high progesterone in women?

• Swollen and tender breasts
• Bloating
• Anxiety
• Tiredness
• Depression
• Low libido
• Weight gain or water retention

What Causes Low Progesterone Levels in Women?

There are several reasons why you may have low progesterone levels, including:

• Anovulatory cycle
• Polycystic Ovary Syndrome (PCOS)
• Stress
• Excessive Exercise
• Underweight or Low Body Fat
• Perimenopause and Menopause
• Hypothyroidism
• Chronic Illness or Inflammatory Conditions
• Ovarian Cysts or Tumours
• Medications
• Endocrine Disruptors

What are the symptoms of low progesterone in women?

The symptoms of low progesterone in women who aren’t pregnant include:

• Irregular periods and shorter menstrual cycles
• Premenstrual spotting
• Heavy or abnormal periods
• Mood changes, anxiety, and depression
• Sleep disturbances
• Difficulty getting pregnant
• Headaches or migraines
• Recurrent miscarriages^[12]

Symptoms of low progesterone during pregnancy are:

• Spotting
• Miscarriage
• Ectopic pregnancy

Does low progesterone cause belly fat?

In some people, low progesterone levels can give way to oestrogen dominance, where oestrogen levels are high compared to progesterone. One of the side effects is weight gain. The loss of oestrogen during menopause is associated with the accumulation of belly fat^[13].

How to Increase Your Progesterone Levels Naturally?

You may want to increase your progesterone levels, especially if trying to conceive. Although there isn’t enough evidence on the effect of naturally increasing progesterone and you should discuss your options with your doctor, there are some things you can do to support hormone balance.

Eating a healthy balanced diet that incorporates healthy fats and low amounts of processed foods and sugar is advisable. Some natural foods may also stimulate the body’s natural progesterone production, such as:

• Beans
• Broccoli
• Cabbage
• Cauliflower
• Kale
• Spinach
• Wholegrains

It’s also important to get plenty of exercise because this can promote a healthy body weight and reduce stress levels, both are risk factors for low progesterone. However, you mustn’t overdo it because excessive exercise can negatively impact your hormones, so it is important to get the balance right for you.

When to consider HRT

You should consider hormone replacement therapy as soon as you start experiencing perimenopause symptoms. However, the decision to use HRT should be discussed with your doctor and should consider the risks and benefits. You can find out more about HRT by reading our guide.

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.