Fertility Advanced - Fertility Hormones

Published: 29/09/2022

The hormones that affect fertility throughout the menstrual cycle

The Fertility Hormones 

Throughout a woman’s menstrual cycle, the hormones that play a vital role within the reproductive system fluctuate. 

The key hormones are:

Follicle Stimulating Hormone (FSH)

Produced in the pituitary gland, FSH stimulates the growth of the follicles in the ovaries during the first half of the cycle, known as the follicular phase. 

A high FSH during the first couple of days of a cycle can indicate a perimenopausal state, as the brain produces more FSH to try to recruit a follicle and produce more oestrogen. A low level can occur in women who experience irregular ovulation, or who do not ovulate.


Oestrogen and progesterone are hormones produced by the ovaries. During the menstrual cycle, a woman’s oestrogen levels naturally rise as a result of being released by growing follicles. 

This rise in oestrogen also results in the endometrium becoming thickened in preparation of implantation of an embryo, and of the promotion of mucus secretion, which is useful to help the sperm along. The surge in oestrogen prompts the pituitary gland to produce Luteinizing Hormone (LH).

Luteinizing Hormone (LH)

The production of LH is stimulated by the release of gonadotropin-releasing hormone (GnRH) by the hypothalamus. 

LH causes the egg to be realised from the ovary (ovulation), rising during the first half of the cycle. This usually occurs around two weeks into a women’s cycle but this can vary. 

Once the egg has been released, the LH stimulates the corpus luteum, resulting in the production of the hormone progesterone. This is known as the luteal phase. LH surges can be tested at home using ovulation kits.


The production and rise of progesterone stops the endometrium from becoming thicker and prepares the uterus for the implantation of an embryo. 

If the egg is fertilised, progesterone levels will continue to rise and the production will come from the placenta, helping to maintain the pregnancy. However, if no fertilisation occurs then the levels drop and the cycle starts again.

Thyroid Stimulating Hormone (TSH)

Produced by the pituitary gland, the role of TSH is to regulate the production of hormones by the thyroid gland, which are essential in energy production regulating metabolism, and oxygen utilisation. 

Everybody produces TSH and it is well established that optimum levels are different for those who are trying to conceive or are pregnant, than those who are not. Research has shown the TSH levels for conception should be equal or lower than 2.5 mIU/L. TSH levels above this have been associated with reduced fertility and miscarriage. 

Recent research has indicated that testing of thyroid antibodies may allow the threshold for TSH levels to be slightly higher than this. Sub-optimal levels can present themselves as tiredness, heavy periods, and feeling very cold. 

Ideally when levels are tested, the whole profile should be taken to include T3 and T4. Like all hormones, TSH levels may fluctuate slightly, and there has been some research that suggests there may be an increase during FSH stimulation as this causes a stress on the hormones. The levels can be corrected with medication.

Anti-mullerian Hormone (AMH)

This protein hormone is produced by the granulosa cells within the ovaries and corresponds to a woman’s egg reserve. The levels will usually decline as we get older. The blood test can be performed by itself, but is usually accompanied by an antral-follicle count (AFC) scan to get an overall picture of a woman's fertility at that time.

If you have any concerns about your hormones, a blood test can be taken to check their levels.

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