Infertility Check Male Blood Test

Follicle Stimulating Hormone (FSH) is produced by the pituitary gland and is essential for male fertility. In men, FSH acts on the Sertoli cells within the seminiferous tubules of the testes—these are the "nurse cells" that support, nourish, and regulate the development of sperm cells (spermatogenesis). Without adequate FSH stimulation, sperm production is impaired. FSH levels in men are regulated by a feedback loop involving inhibin B (produced by Sertoli cells) and testosterone. When sperm production is healthy, inhibin B signals the pituitary to maintain moderate FSH output. When there's damage to the seminiferous tubules or impaired spermatogenesis, inhibin B production falls and FSH rises—the pituitary is "trying harder" to stimulate sperm production. This makes FSH a useful marker of testicular function and spermatogenesis. Normal FSH levels in men are typically between 1-12 IU/L. Elevated FSH (above 10-12 IU/L) often indicates primary testicular failure—the testes themselves are not producing sperm adequately despite adequate stimulation. This can result from conditions such as previous testicular injury or torsion, chemotherapy or radiation, infections (mumps orchitis), varicocele, genetic conditions (Klinefelter syndrome), or idiopathic (unexplained) testicular failure. Very high FSH levels generally indicate severe damage to sperm-producing tissue and may predict a poor response to fertility treatment. Conversely, low FSH combined with low LH and low testosterone suggests a problem at the level of the pituitary or hypothalamus (secondary hypogonadism), which may be more amenable to hormonal treatment. 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 plays a different but complementary role to FSH in male reproduction. While FSH acts on Sertoli cells to support sperm production, LH acts on Leydig cells in the testes to stimulate testosterone production. Testosterone is essential not only for sperm production (it acts locally within the testes at high concentrations) but also for libido, erectile function, muscle mass, bone density, and general male health. LH and testosterone exist in a feedback loop: when testosterone is adequate, it signals the pituitary to reduce LH output. When testosterone is low (whether due to testicular problems or other causes), LH rises as the pituitary attempts to stimulate more testosterone production. This feedback relationship helps distinguish between different causes of testosterone deficiency. Normal LH levels in men are typically between 2-12 IU/L. Elevated LH with low testosterone indicates primary hypogonadism—the testes are not producing adequate testosterone despite strong stimulation from the pituitary. This pattern is seen in testicular damage, Klinefelter syndrome, and age-related testicular decline. Low LH with low testosterone indicates secondary hypogonadism—the problem lies with the pituitary or hypothalamus, which is not sending adequate stimulation signals. This can be caused by pituitary tumours (including prolactinomas), medications (opioids, steroids), obesity, or severe illness. Secondary hypogonadism is often more responsive to treatment than primary. Normal LH with low testosterone may indicate a subtle or early problem. Results outside the normal range may need a follow-up with your GP or a fertility specialist.

Sex Hormone Binding Globulin (SHBG) is a protein produced primarily by the liver that binds to sex hormones—testosterone, dihydrotestosterone (DHT), and oestradiol—and transports them through the bloodstream. SHBG binds testosterone very tightly, and testosterone that is bound to SHBG is considered biologically inactive because it cannot enter cells to exert its effects. Only the "free" testosterone (about 2-3% of total) plus the testosterone loosely bound to albumin is considered bioavailable. SHBG levels significantly affect how much of your total testosterone is actually available for your body to use. Two men with identical total testosterone levels can have very different amounts of bioavailable testosterone depending on their SHBG levels. High SHBG means more testosterone is bound and unavailable, effectively reducing the testosterone your body can use. Low SHBG means more testosterone is free and available. Normal SHBG levels in men vary but are typically between 15-55 nmol/L. SHBG is increased by ageing, liver disease, hyperthyroidism, low body weight, and certain medications (anticonvulsants). SHBG is decreased by obesity, insulin resistance and type 2 diabetes, hypothyroidism, high androgen levels, and anabolic steroid use. Understanding SHBG is crucial for interpreting testosterone results—a man with high-normal total testosterone but high SHBG may actually have low bioavailable testosterone and experience symptoms of testosterone deficiency. This is why this test includes the Free Androgen Index (FAI), which accounts for SHBG. Results outside the normal range may need a follow-up with your GP.

The Free Androgen Index (FAI) is a calculated ratio that estimates the amount of biologically active testosterone in your blood. It's calculated by dividing total testosterone by SHBG and multiplying by 100: FAI = (Total Testosterone / SHBG) × 100. This provides a clinically useful estimate of "free" or bioavailable testosterone without requiring the more complex and expensive direct measurement of free testosterone. The FAI accounts for the effect of SHBG on testosterone availability. Because SHBG binds testosterone tightly and renders it inactive, total testosterone alone doesn't tell the whole story. A man with normal total testosterone but high SHBG may have a low FAI—indicating that despite adequate total testosterone production, not enough is available for his body to use. Conversely, a man with borderline total testosterone but low SHBG may have an adequate FAI. In healthy adult men, typical FAI values range from approximately 30-150. Values below 30 may indicate testosterone deficiency (either from inadequate production or excessive binding by SHBG), which can contribute to reduced fertility, low libido, erectile dysfunction, fatigue, reduced muscle mass, and osteoporosis. The FAI should be interpreted alongside the individual testosterone and SHBG values, as well as FSH, LH, and clinical symptoms. Note that while FAI is useful for screening and monitoring, it's an estimate—if results are borderline or don't match your clinical picture, direct measurement of free testosterone by equilibrium dialysis may be warranted. 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. While it's best known for its role in stimulating breast milk production in women, prolactin also affects male reproductive function. In men, prolactin helps regulate the function of Leydig cells (which produce testosterone) and influences libido and sexual function. Normal prolactin levels in men are typically between 50-350 mU/L (or approximately 2.5-17 ng/mL, depending on the assay). Elevated prolactin (hyperprolactinaemia) in men can suppress the release of GnRH (gonadotropin-releasing hormone) from the hypothalamus, which in turn reduces LH and FSH secretion from the pituitary. This leads to decreased testosterone production (secondary hypogonadism) and can impair sperm production. Men with hyperprolactinaemia may experience reduced libido, erectile dysfunction, infertility, and sometimes breast enlargement (gynaecomastia) or galactorrhoea (nipple discharge). Mildly elevated prolactin (below 25-30 ng/mL or approximately 500-600 mU/L) is often not clinically significant and may result from stress, recent food intake, or sample collection conditions. However, significantly elevated prolactin (above 30 ng/mL) warrants investigation. The most common cause is a prolactinoma—a benign pituitary tumour that secretes prolactin. Larger prolactinomas (macroadenomas >10mm) may also cause headaches and visual field disturbances by pressing on nearby structures. Fortunately, prolactinomas respond very well to medication (dopamine agonists like cabergoline), which can normalise prolactin, restore testosterone levels, and improve fertility. Other causes of elevated prolactin include certain medications (particularly antipsychotics, metoclopramide), hypothyroidism, kidney disease, and chest wall irritation. If prolactin is elevated, repeat testing and potentially pituitary MRI imaging is usually recommended. Results outside the normal range may need a follow-up with your GP or an endocrinologist.