Female Infertility Check Blood test

Follicle Stimulating Hormone (FSH) is produced by the pituitary gland in the brain and plays a crucial role in female reproduction. As its name suggests, FSH stimulates the growth and development of ovarian follicles—the fluid-filled sacs in the ovaries that contain eggs. Each month, FSH prompts several follicles to begin developing, and as they grow, they produce oestradiol. Eventually, one follicle becomes dominant and releases a mature egg at ovulation. Baseline FSH levels (measured on day 2-3 of the menstrual cycle) are one of the most commonly used markers of ovarian reserve—an indication of how many eggs remain in your ovaries and how well they may respond to stimulation. The feedback loop works like this: when ovarian reserve is good and follicles respond readily to FSH, the ovaries produce adequate oestradiol, which signals the pituitary to keep FSH production moderate. When ovarian reserve is diminished and follicles respond less well, the pituitary compensates by producing more FSH—essentially "stepping on the gas" to try to stimulate the remaining follicles. Normal day 2-3 FSH levels are typically between 3-10 IU/L. Levels above 10 IU/L may suggest reduced ovarian reserve, and levels above 15-20 IU/L often indicate significantly diminished reserve. However, FSH must be interpreted alongside oestradiol (a high oestradiol can artificially suppress FSH, masking reduced reserve) and in the context of your age—ovarian reserve naturally declines with age, and a given FSH level means different things at 28 versus 42. Persistently elevated FSH above 25-40 IU/L, combined with absent periods and low oestradiol, is consistent with menopause or premature ovarian insufficiency. Results outside the normal range may need a follow-up with your GP or a fertility specialist.

Luteinising Hormone (LH) is produced by the pituitary gland and works alongside FSH to regulate the menstrual cycle and ovulation. While FSH stimulates follicle growth in the first half of the cycle, LH triggers ovulation—the release of a mature egg from the dominant follicle. The dramatic surge in LH that occurs mid-cycle (the "LH surge") is what home ovulation predictor kits detect. After ovulation, LH also stimulates the empty follicle to transform into the corpus luteum, which produces progesterone to support early pregnancy. Baseline LH levels (measured on day 2-3) are typically similar to or slightly lower than FSH, usually between 2-10 IU/L. The ratio of LH to FSH provides additional diagnostic information. In healthy women, the LH: FSH ratio is typically around 1:1 or slightly less. An elevated LH: FSH ratio (often 2:1 or 3:1) is characteristic of polycystic ovary syndrome (PCOS), one of the most common causes of anovulatory infertility. In PCOS, tonically elevated LH disrupts the normal hormonal signalling needed for regular ovulation. Very low LH levels may indicate a problem with the pituitary gland or hypothalamus (hypothalamic amenorrhoea), which can occur with extreme weight loss, excessive exercise, or severe stress. Like FSH, persistently elevated LH combined with absent periods may indicate menopause or premature ovarian insufficiency. Results should be interpreted alongside FSH, oestradiol, and your clinical picture. Results outside the normal range may need a follow-up with your GP or a fertility specialist.

Oestradiol (also spelled estradiol, abbreviated E2) is the most potent form of oestrogen and the primary oestrogen produced by the ovaries during reproductive years. It's produced by the granulosa cells of developing ovarian follicles in response to FSH stimulation. Oestradiol levels rise as follicles develop during the first half of the menstrual cycle (follicular phase), peak just before ovulation, drop briefly, then rise again during the second half (luteal phase) before falling to trigger menstruation if pregnancy doesn't occur. Baseline oestradiol (measured on day 2-3) should be relatively low—typically below 200 pmol/L (or approximately 55 pg/mL). If oestradiol is elevated early in the cycle, this may indicate an ovarian cyst, early follicle recruitment, or declining ovarian reserve. Importantly, an elevated baseline oestradiol can artificially suppress FSH levels, making FSH appear normal when ovarian reserve is actually diminished. This is why oestradiol and FSH should always be interpreted together. Very low oestradiol levels combined with elevated FSH indicate ovarian insufficiency or menopause—the ovaries are no longer producing adequate oestrogen despite high FSH stimulation. Low oestradiol with low FSH and LH suggests a problem at the level of the pituitary or hypothalamus (hypogonadotropic hypogonadism). Normal oestradiol with an elevated LH: FSH ratio may be seen in PCOS. Oestradiol is also important beyond fertility—adequate levels are needed for bone health, cardiovascular protection, and general wellbeing. Results outside the normal range may need a follow-up with your GP or a fertility specialist.

Prolactin is a hormone produced primarily by the pituitary gland. Its main function is to stimulate breast milk production after childbirth, but it also plays important roles in reproductive function even outside of pregnancy and breastfeeding. In non-pregnant, non-breastfeeding women, prolactin levels should be relatively low—typically below 500-600 mU/L (or approximately 25 ng/mL, depending on the assay). Elevated prolactin (hyperprolactinaemia) is an important and treatable cause of infertility. High prolactin suppresses the release of GnRH (gonadotropin-releasing hormone) from the hypothalamus, which in turn reduces FSH and LH secretion from the pituitary. This disrupts the normal hormonal signals needed for follicle development and ovulation. Women with hyperprolactinaemia may experience irregular periods, absent periods (amenorrhoea), milky nipple discharge (galactorrhoea) even without pregnancy, and difficulty conceiving. The most common cause of significantly elevated prolactin is a prolactinoma—a benign (non-cancerous) tumour of the pituitary gland that secretes prolactin. Fortunately, prolactinomas are usually easily treated with medication (dopamine agonists like cabergoline or bromocriptine), which can normalise prolactin levels, restore ovulation, and allow conception. Other causes of elevated prolactin include certain medications (particularly some antipsychotics and anti-nausea drugs), hypothyroidism, and sometimes PCOS. Mildly elevated prolactin can also result from stress, recent nipple stimulation, or blood sampling conditions—this is why morning sampling after rest is important. If prolactin is elevated, repeat testing and further investigation (possibly including pituitary imaging) is usually recommended. Results outside the normal range may need a follow-up with your GP or an endocrinologist.