Gonadotropins and Sex Steroids

Luteinising hormone (LH) and follicle stimulating hormone (FSH) are pituitary glycoproteins released in pulses under hypothalamic gonadotropin releasing hormone. They drive gonadal function: in women, FSH stimulates follicle growth and oestradiol production, and an LH surge triggers ovulation and progesterone production. In men, LH stimulates testosterone production by Leydig cells, and FSH supports spermatogenesis.

Sex steroids (oestradiol, progesterone, testosterone) feed back to the hypothalamus and pituitary. Sex hormone binding globulin (SHBG) binds testosterone and oestradiol and controls the free fraction. All are measured by immunoassay, with mass spectrometry preferred for low testosterone and oestradiol. Anti-Müllerian hormone (AMH) from ovarian follicles reflects ovarian reserve.

The panel diagnoses hypogonadism and its level (primary or central), menstrual disturbance, subfertility, polycystic ovary syndrome, menopause, delayed or precocious puberty, and androgen excess.

Male hypogonadism affects about 2 to 6% of middle aged men, and the Klinefelter syndrome affects about 1 in 600 males. Polycystic ovary syndrome affects 6 to 13% of women of reproductive age. Primary ovarian insufficiency affects about 1% of women under 40 years. Infertility affects about 1 in 7 couples.

Indications. Amenorrhoea or oligomenorrhoea, subfertility, menopausal symptoms, hirsutism and acne, virilisation, delayed or precocious puberty, low libido, erectile dysfunction, gynaecomastia, osteoporosis in young adults, pituitary disease, testicular failure, monitoring of fertility treatment, and testosterone therapy.

Specimen. Serum. In men, testosterone is measured fasting between 7 and 11 am, because levels fall by 20 to 30% through the day and after a meal. In menstruating women, FSH, LH and oestradiol are taken on days 2 to 5 of the cycle, progesterone about 7 days before the expected next period (day 21 of a 28-day cycle), and testosterone on days 2 to 5. Record the day of cycle, hormonal contraception and medicines.

Reference ranges depend on sex, age, cycle phase and assay. Local ranges take precedence.

FSH. Women, early follicular phase: 3 to 10 IU/L. Postmenopausal: over 25 to 30 IU/L, usually 30 to 120. Men: 1.5 to 12 IU/L. Raised: primary gonadal failure (menopause, primary ovarian insufficiency, Turner syndrome, Klinefelter syndrome, orchitis, chemotherapy and radiotherapy, bilateral orchidectomy), and rarely FSH-secreting tumours. Lowered: hypothalamic or pituitary disease, hyperprolactinaemia, pregnancy, hormonal contraception, anorexia and weight loss, and anabolic steroid use.

LH. Women, follicular phase: 2 to 10 IU/L, with a mid-cycle peak of 20 to 80 IU/L. Postmenopausal: over 15 IU/L. Men: 1.5 to 9 IU/L. Raised: primary gonadal failure, polycystic ovary syndrome (LH to FSH ratio over 2), the ovulatory surge, and precocious puberty. Lowered: central hypogonadism and exogenous sex steroids.

Oestradiol. Women, early follicular phase: 100 to 200 pmol/L (30 to 55 pg/mL), mid-cycle peak 500 to 1500 pmol/L, postmenopausal under 100 pmol/L. Men: under 150 pmol/L. Raised: pregnancy, ovarian hyperstimulation, oestrogen secreting tumours, liver disease, obesity, and oestrogen therapy. Lowered: menopause, primary ovarian insufficiency, hypothalamic amenorrhoea, and Turner syndrome. Used to follow ovulation induction.

Progesterone. Luteal phase: over 30 nmol/L (over 10 ng/mL) in a mid-luteal sample confirms ovulation. Follicular phase: under 3 nmol/L. Raised in pregnancy, luteal cysts, congenital adrenal hyperplasia and some tumours. Low values after day 21 suggest anovulation.

Testosterone. Men: total 10 to 35 nmol/L (about 300 to 1000 ng/dL), with a lower limit of about 10 to 12 nmol/L. Women: 0.3 to 2.0 nmol/L. Raised in women: polycystic ovary syndrome (commonly 2 to 5 nmol/L), congenital adrenal hyperplasia, androgen secreting tumours (over 5 nmol/L), anabolic steroid or testosterone use, and hyperprolactinaemia. Lowered in men: primary hypogonadism, central hypogonadism, obesity, diabetes, opioids, chronic illness, ageing, and glucocorticoids.

SHBG. Men: 10 to 57 nmol/L. Women: 20 to 130 nmol/L. Raised: hyperthyroidism, oestrogens, cirrhosis, ageing, HIV, anticonvulsants. Lowered: obesity, insulin resistance, hypothyroidism, nephrotic syndrome, androgens, acromegaly, and Cushing syndrome. Free or bioavailable testosterone is calculated from total testosterone, SHBG and albumin when SHBG is abnormal.

Anti-Müllerian hormone. Women: 2 to 6 microg/L (14 to 43 pmol/L) in the reproductive years, falling to undetectable at menopause. Low values indicate reduced ovarian reserve, and high values (over 3.5 to 5 microg/L) are found in polycystic ovary syndrome. It can be taken on any day of the cycle.

Women.

• Primary ovarian insufficiency: amenorrhoea before 40 years, FSH over 25 to 40 IU/L on two samples at least 4 weeks apart, low oestradiol. Causes: autoimmune, Turner syndrome, fragile X premutation, chemotherapy, radiotherapy, surgery.
• Menopause: FSH and LH high, oestradiol low. FSH is not needed for diagnosis over 45 years with typical symptoms.
• Hypothalamic amenorrhoea: low or normal FSH and LH with low oestradiol (weight loss, excess exercise, stress, eating disorders).
• Hyperprolactinaemia and pituitary disease: low FSH and LH with raised prolactin, or other pituitary deficits.
• Polycystic ovary syndrome: raised or high normal LH, normal FSH, mildly raised testosterone, low SHBG, raised AMH, and exclusion of other causes.
• Androgen excess: total testosterone over 5 nmol/L suggests a tumour, and 17-hydroxyprogesterone and DHEA sulphate screen for adrenal causes.

Men.

• Primary hypogonadism: low testosterone with high LH and FSH (Klinefelter syndrome, orchitis, torsion, cryptorchidism, chemotherapy, radiotherapy).
• Central hypogonadism: low testosterone with low or inappropriately normal LH and FSH (pituitary tumour, hyperprolactinaemia, Kallmann syndrome, opioids, anabolic steroid use, obesity, illness).
• Diagnosis of hypogonadism needs symptoms plus a low morning testosterone on two occasions (under 8 to 10 nmol/L clearly low, and 8 to 12 nmol/L borderline needing free testosterone).
• Male infertility: isolated high FSH with small testes and azoospermia suggests testicular failure, and normal FSH suggests obstruction.

Puberty.

• Delayed puberty: constitutional (low gonadotropins and testosterone with normal later progression), hypogonadotropic (Kallmann syndrome, pituitary disease), or hypergonadotropic (Turner and Klinefelter syndromes).
• Precocious puberty: raised LH after a GnRH stimulation test (central), or low LH with high sex steroids (peripheral, from tumour, congenital adrenal hyperplasia or McCune-Albright syndrome).

Ovulation and fertility. Mid-luteal progesterone over 30 nmol/L, AMH and day 3 FSH for ovarian reserve, and LH kits for timing.

Critical values and findings needing immediate action.

• Total testosterone over 5 nmol/L in a woman, or rapid virilisation, which needs imaging for ovarian or adrenal tumour.
• Panhypopituitarism with hypotension or hyponatraemia (cortisol first).
• Very low oestradiol with bone loss in a young woman.
• Oestradiol very high with abdominal distension, breathlessness or oliguria after ovulation induction (ovarian hyperstimulation).
• Testosterone very high with polycythaemia in a man using androgens.

Interferences and pitfalls.

• Hormonal contraception, hormone replacement and pregnancy suppress or distort results, and levels are interpreted off treatment if safe.
• Cycle timing changes every value in women, and a random sample is difficult to interpret.
• Immunoassays for testosterone and oestradiol are inaccurate at low concentrations (women, children, men on treatment), and mass spectrometry is better.
• Biotin interferes with some immunoassays.
• Acute illness, obesity, opioids and glucocorticoids lower testosterone, and a single low value is repeated.
• Total testosterone is misleading when SHBG is abnormal.
• Heterophile antibodies cause false results, and FSH and LH can be raised by cross-reaction with hCG.
• Testosterone therapy suppresses LH, FSH and spermatogenesis.

Special groups.

• Neonates and infants: a transient surge of gonadotropins and sex steroids occurs in the first 6 months (mini puberty).
• Children: age specific and Tanner-stage-specific ranges are needed, and the GnRH stimulation test confirms central precocious puberty.
• Pregnancy: oestradiol and progesterone rise greatly, and the tests are not used for hypogonadism.
• Older adults: testosterone falls about 1% a year, and symptoms must be present before a diagnosis of late onset hypogonadism.
• Regions: mumps orchitis, malnutrition and schistosomiasis affect gonadal function in some settings.

Follow up tests. Repeat morning testosterone, free testosterone, prolactin, thyroid function tests, pregnancy test, karyotype, FMR1 premutation, adrenal antibodies, 17-hydroxyprogesterone, DHEA sulphate, androstenedione, pelvic and testicular ultrasound, semen analysis, pituitary MRI, other pituitary hormones, bone density, and GnRH stimulation.