Female Hormone Blood Test Kit

Follicle stimulating hormone is produced by the pituitary gland in the brain and is essential for reproductive function. In women, FSH stimulates the growth and development of ovarian follicles—the fluid-filled sacs that contain eggs. As follicles develop, they produce oestrogen. FSH levels vary throughout the menstrual cycle: they're highest at the beginning of the cycle (follicular phase) to recruit follicles, drop mid-cycle as the dominant follicle takes over, and remain low in the second half (luteal phase). FSH is a key marker for assessing ovarian reserve and menopausal status. As ovarian reserve declines with age, the pituitary produces more FSH in an attempt to stimulate the ovaries—so rising baseline FSH (measured on days 2-5 of the cycle) indicates diminishing ovarian reserve. Very high FSH (typically above 25-40 IU/L) with low oestradiol indicates menopause or premature ovarian insufficiency. In PCOS, FSH is often normal or low relative to LH. Results outside the normal range may need a follow-up with your GP.

Luteinising hormone is produced by the pituitary gland and works alongside FSH to regulate the menstrual cycle and ovulation. LH levels remain relatively low during most of the cycle but surge dramatically mid-cycle—this LH surge triggers ovulation, causing the mature follicle to rupture and release the egg. After ovulation, LH stimulates the empty follicle to become the corpus luteum, which produces progesterone. The ratio of LH to FSH is clinically useful. In a normal cycle, the LH: FSH ratio is approximately 1:1. In PCOS, this ratio is often elevated (2:1 or higher), with LH disproportionately high compared to FSH. This elevated LH contributes to excess androgen production by the ovaries, causing symptoms like acne, hirsutism (excess hair growth), and irregular periods. Like FSH, LH rises after menopause due to loss of negative feedback from the ovaries. Results outside the normal range may need a follow-up with your GP.

Oestradiol is the primary and most potent form of oestrogen, produced mainly by the developing follicles in the ovaries. It's responsible for the development of female secondary sexual characteristics, regulation of the menstrual cycle, maintenance of the uterine lining, bone health, cardiovascular protection, skin health, and brain function. Oestradiol also has significant effects on mood and cognitive function. Oestradiol levels fluctuate significantly throughout the menstrual cycle. They're lowest at the start of menstruation, rise progressively as follicles develop (peaking just before ovulation), drop briefly after ovulation, then rise again in the mid-luteal phase before falling if pregnancy doesn't occur. Baseline oestradiol (days 2-5) should be relatively low; an elevated baseline can indicate diminished ovarian reserve or ovarian cysts. After menopause, oestradiol falls dramatically to very low levels. Low oestradiol causes menopausal symptoms including hot flushes, night sweats, vaginal dryness, and contributes to bone loss. Results outside the normal range may need a follow-up with your GP.

Although primarily known as a male hormone, testosterone is also important for women's health. In women, testosterone is produced in smaller amounts by the ovaries and adrenal glands. It contributes to libido (sexual desire), energy levels, muscle mass and strength, bone density, mood, and cognitive function. Testosterone levels in women are about 10-20 times lower than in men. Elevated testosterone in women is one of the hallmarks of PCOS and can cause symptoms including acne, hirsutism (excess facial and body hair), scalp hair thinning (androgenic alopecia), and menstrual irregularities. Testosterone is also elevated in other conditions affecting the ovaries or adrenal glands. Conversely, low testosterone can contribute to reduced libido, fatigue, low mood, and reduced muscle mass—symptoms that can occur around menopause when testosterone levels naturally decline. Testosterone should be interpreted alongside SHBG and Free Androgen Index for a complete picture. Results outside the normal range may need a follow-up with your GP.

Prolactin is a hormone produced by the pituitary gland that's primarily known for stimulating milk production (lactation) after childbirth. However, prolactin has over 300 known functions in the body and plays a role in immune function, metabolism, and reproductive regulation. In non-pregnant, non-breastfeeding women, prolactin should be at relatively low levels. Elevated prolactin (hyperprolactinaemia) can disrupt the menstrual cycle by suppressing FSH and LH, leading to irregular or absent periods, anovulation (failure to ovulate), and infertility. High prolactin can also cause galactorrhoea (breast milk production outside of pregnancy/breastfeeding). Causes include pituitary tumours (prolactinomas—usually benign), certain medications (particularly antipsychotics, some antidepressants, and anti-nausea drugs), hypothyroidism, kidney disease, and stress. Prolactin is very sensitive to timing—levels are elevated during sleep and immediately upon waking, and can rise with stress, nipple stimulation, or recent sexual activity. The test should be taken at least 1 hour after waking. Results outside the normal range may need a follow-up with your GP.

Sex hormone binding globulin is a protein produced by the liver that binds to sex hormones—primarily testosterone and oestradiol—and transports them through the bloodstream. Importantly, when hormones are bound to SHBG, they're biologically inactive; only the 'free' (unbound) hormone can enter cells and exert effects. SHBG therefore acts as a buffer, regulating how much active hormone is available to tissues. SHBG levels are influenced by many factors. Oestrogen increases SHBG production (so levels are higher in women than men, and rise during pregnancy and with oestrogen-containing contraceptives). Thyroid hormones also increase SHBG. Conversely, insulin resistance, obesity, and androgens suppress SHBG production. In PCOS, low SHBG is common—this means more testosterone is free and bioavailable, contributing to hyperandrogenic symptoms even if total testosterone isn't dramatically elevated. Low SHBG is also associated with metabolic syndrome and increased cardiovascular risk. High SHBG can cause symptoms of hormone deficiency despite normal total hormone levels. Results outside the normal range may need a follow-up with your GP.

The Free Androgen Index is a calculated ratio of total testosterone to SHBG, expressed as a percentage. It provides an estimate of bioavailable (free) testosterone—the testosterone that's actually available to enter cells and have biological effects. FAI = (Total Testosterone ÷ SHBG) × 100. FAI is particularly useful in women because it can reveal excess androgen activity even when total testosterone is within the normal range. If SHBG is low (as it often is in PCOS, obesity, or insulin resistance), more testosterone is free and bioavailable, and FAI will be elevated. A high FAI helps confirm biochemical hyperandrogenism, one of the diagnostic criteria for PCOS. Normal FAI in women is typically below 5-8% (varies by laboratory). An elevated FAI helps explain symptoms like acne, hirsutism, and scalp hair loss even when total testosterone appears normal. Results outside the normal range may need a follow-up with your GP.

Thyroid stimulating hormone is produced by the pituitary gland to regulate the thyroid—a butterfly-shaped gland in the neck that controls metabolism and affects virtually every organ system. TSH stimulates the thyroid to produce thyroid hormones (T4 and T3). It works through a negative feedback loop: when thyroid hormone levels are low, TSH rises to stimulate more production; when thyroid hormones are adequate, TSH falls. TSH is the most sensitive initial test for thyroid dysfunction. An elevated TSH indicates hypothyroidism (underactive thyroid)—the pituitary is working harder to stimulate an underperforming thyroid. A suppressed TSH indicates hyperthyroidism (overactive thyroid). Thyroid disorders are much more common in women and significantly affect reproductive health: hypothyroidism can cause heavy or irregular periods, anovulation, fertility problems, and increased miscarriage risk; hyperthyroidism can cause light or absent periods. Even subclinical hypothyroidism (elevated TSH with normal T4) may affect fertility and pregnancy outcomes. Thyroid dysfunction can also cause symptoms that mimic other conditions—fatigue, weight changes, mood changes, and hair loss. Results outside the normal range may need a follow-up with your GP.

Free thyroxine (Free T4) is the unbound, biologically active form of the main thyroid hormone T4. Most T4 in the blood is bound to carrier proteins and inactive; only the small 'free' fraction can enter cells and exert effects. T4 is the primary hormone produced by the thyroid gland and serves as a reservoir that's converted to the more active T3 in tissues as needed. Free T4 is measured alongside TSH to confirm and characterise thyroid dysfunction. In primary hypothyroidism, TSH is elevated and Free T4 is low (the thyroid isn't producing enough hormone). In primary hyperthyroidism, TSH is suppressed and Free T4 is elevated (the thyroid is overproducing). Subclinical hypothyroidism shows elevated TSH with normal Free T4—the pituitary is working harder to maintain normal thyroid hormone levels. Free T4 is preferred over total T4 because it's not affected by changes in binding proteins (which can occur with oestrogen, pregnancy, or certain medications). Normal Free T4 with abnormal TSH suggests early or subclinical thyroid dysfunction. Results outside the normal range may need a follow-up with your GP.