Key Female Fertility Hormones
The key female fertility hormones are:
- Anti-Mullerian Hormone (AMH)
- Follicle-Stimulating Hormone (FSH)
- Luteinising Hormone (LH)
- Oestradiol (oestrogen)
Age is a direct factor affecting female fertility. On average, females are most fertile in their early 20s and fertility begins to decline during their mid-30s. Before we look at the key fertility hormones, it is a good idea to get to know the phases of the menstrual cycle:
The follicular or proliferative phase
This phase starts on the first day of your menstrual cycle and ends with ovulation (the release of an egg from the ovary). FSH stimulates the production of oestradiol by the follicle and both these hormones work together to develop the egg follicle further. The average length of the follicular stage is around 16 days but is dependent on how long it takes for one dominant egg follicle to emerge.
The luteal or secretory phase
This phase begins after an egg has been released from the ovary and lasts for around 14 days. The luteal phase ends just before your menstrual period. Progesterone is produced during this time after the follicle ruptures and releases its egg, forming the hormone-producing structure known as the corpus luteum.
Hormonal imbalances can cause female infertility and each of the above hormones have key roles in helping a woman to conceive.
Our female hormone blood test checks levels of a range of key hormones that affect fertility.
Anti-Mullerian Hormone (AMH)
AMH is a protein hormone which is secreted by cells in developing eggs and is a good indicator of a female’s ovarian reserve. Females are born with their lifetime supply of eggs which decreases with age. A girl may have around 2,000,000 eggs but at the time of puberty or adolescence, this will have fallen to around 400,000. By the age of 37, her egg count could be as low as 25,000, indicating why it can be harder to fall pregnant as you get older.
Previously, AMH was known for its role in male sex differentiation as it is secreted by the testicular Sertoli cells around the 7th week of gestation. However, it’s use in determining the female ovarian reserve can help to diagnose a premature loss of fertility in young women or show the natural decline in older females.
FOLLICLE STIMULATING HORMONE (FSH)
FSH is produced by the pituitary gland, a tiny organ located at the base of the brain. It is no bigger than the size of a pea but is known as the “master gland” because it produces so many of the hormones the body requires for normal functioning.
“Follicle stimulating hormone (FSH) is produced by the pituitary gland and is one of the main hormones responsible for follicle growth (and ensuing egg production),” explains Dr Suvir Venkataraman BEng (Hons), PhD and general manager at the Harley Street Fertility Clinic.
The growth and development of unfertilised eggs, also known as ovarian follicles during the follicular stage of the menstrual cycle is stimulated by FSH. The hormone is also important to produce oestradiol by the follicle and together they help the follicle to develop further.
Progesterone is produced during the luteal phase of the menstrual cycle because of FSH. FSH production is controlled by both oestradiol and progesterone.
LUTEINISING HORMONE (LH)
LH is another hormone produced by the pituitary gland. Dr Venkataraman explains, “luteinising hormone in combination with FSH acts to induce final maturation of the egg and subsequent ovulation.”
The splitting of the menstrual cycle into two phases can be characterised by a mid-cycle surge in both FSH and LH which triggers the release of the egg from an ovary. Ovulation stimulates the production of the corpus luteum which produces progesterone, a hormone needed to sustain a pregnancy.
Therefore, FSH and LH work together to trigger ovulation and progesterone by the corpus luteum.
Oestradiol and Progesterone
Oestradiol is a type of oestrogen produced by the ovaries. It is also produced by the testes in men, too. “Oestradiol and progesterone are produced by the ovaries as the follicles grow and are responsible for thickening the endometrium (uterus lining) in preparation for embryo implantation,” says Dr Venkataraman.
Oestradiol helps to promote normal ovulation, conception and pregnancy, but it also ensures healthy bones and helps regulate female cholesterol levels.
Oestrogen causes the lining of the womb, endometrium, to prepare for pregnancy through growth and thickening. When an egg is released, the corpus luteum produces progesterone. The progesterone stops the endometrium from growing any more and gets the uterus prepared for the potential implantation of a fertilised egg.
If the egg isn’t fertilised, then the corpus luteum will degenerate and progesterone levels will fall. However, if pregnancy occurs, progesterone levels will continue to rise. The placenta will later become the main source of progesterone for the duration of the pregnancy, helping to sustain the pregnancy.