LH/FSH Ratio

Reproductive

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The LH/FSH ratio is often used as a diagnostic marker, especially in women with suspected PCOS (Polycystic Ovary Syndrome).

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LH/FSH Ratio - Comprehensive Medical Test Guide

Why is it done?
- Measures the ratio between Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH), two critical pituitary hormones that regulate reproductive function and sex hormone production
- Evaluated to assess gonadal function, ovulatory disorders, and hormonal imbalances in both men and women
- Primary indication in women: Suspected polycystic ovary syndrome (PCOS), irregular menstrual cycles, infertility evaluation, and assessment of ovulatory function
- Primary indication in men: Evaluation of hypogonadism, infertility, testicular dysfunction, and hormonal imbalances
- Performed during initial fertility workup, menstrual cycle abnormalities, suspected endocrine disorders, and delayed or precocious puberty evaluation
- Typically tested in the follicular phase (days 3-5) of the menstrual cycle in women for standardized results
Normal Range
- Normal LH/FSH Ratio in Women (Follicular Phase): 1:1 to 3:1 (typically 1:1 to 2:1)
- Normal LH/FSH Ratio in Men: 0.5:1 to 1:1 (approximately 1:1)
- LH normal range: 1.7-8.6 mIU/mL (follicular phase women), 0.8-7.6 mIU/mL (men)
- FSH normal range: 3.5-12.5 mIU/mL (follicular phase women), 1.4-18.1 mIU/mL (men)
- Units of measurement: mIU/mL (milli-International Units per milliliter) or IU/L (International Units per liter)
- Normal ratio indicates balanced gonadotropin function and normal reproductive hormone production
- Elevated LH/FSH ratio (>3:1 in women) suggests abnormal gonadal function or hormonal imbalance
- Individual lab ranges may vary; results should be interpreted with patient-specific reference values
Interpretation
- Elevated LH/FSH Ratio (>3:1 in women): Strongly suggestive of PCOS; associated with anovulation, insulin resistance, and elevated androgen levels
- Low LH/FSH Ratio (<0.5:1): May indicate hypogonadotropic hypogonadism, hypopituitarism, or primary pituitary dysfunction
- Elevated LH with normal FSH: Suggests androgen excess, ovarian pathology, or PCOS in women; possible Leydig cell dysfunction in men
- Elevated FSH with normal LH: May indicate primary gonadal failure, premature ovarian insufficiency (POI) in women, or primary testicular failure in men
- Elevated both LH and FSH: Indicates primary gonadal dysfunction or failure; in postmenopausal women, both are markedly elevated (>30 mIU/mL)
- Low both LH and FSH: Suggests secondary hypogonadism, including pituitary or hypothalamic dysfunction
- Factors affecting readings: Menstrual cycle phase (peak LH surge mid-cycle), time of day (both hormones show pulsatile secretion), stress, medications, obesity, and recent exercise
- Age affects interpretation: Prepubertal children have lower values; postmenopausal women have significantly elevated values
- Clinical significance: LH/FSH ratio is particularly useful for PCOS diagnosis and differentiating causes of infertility, anovulation, and gonadal dysfunction
- Results must be interpreted in context of clinical symptoms, other hormone levels (testosterone, estradiol, prolactin), and additional diagnostic findings
Associated Organs
- Primary organs: Anterior pituitary gland (source of LH and FSH), hypothalamus (regulator via GnRH), ovaries (in women), and testes (in men)
- Secondary organs: Adrenal glands (produce androgens), thyroid gland (affects metabolic status and hormone metabolism)
- PCOS (Polycystic Ovary Syndrome): Associated with elevated LH/FSH ratio, characterized by ovulatory dysfunction, hyperandrogenism, and insulin resistance; affects approximately 5-20% of women of reproductive age
- Primary ovarian insufficiency (POI): Premature menopause with elevated FSH and LH; associated with autoimmune disorders, genetic conditions, or chemotherapy exposure
- Hypogonadism: Deficiency of sex hormones; primary hypogonadism shows elevated gonadotropins; secondary hypogonadism shows low or normal gonadotropins
- Hyperprolactinemia: Elevated prolactin suppresses GnRH, resulting in low LH and FSH; may cause amenorrhea and infertility
- Pituitary disorders: Pituitary adenomas, pituitary insufficiency, or Sheehan syndrome result in low or abnormal LH/FSH ratios
- Infertility: Abnormal LH/FSH ratios contribute to both male and female infertility through multiple mechanisms including anovulation and poor sperm production
- Thyroid disorders: Hypothyroidism and hyperthyroidism can alter LH/FSH secretion and affect reproductive function
- Potential complications: Chronic anovulation leading to endometrial hyperplasia, increased cardiovascular disease risk in PCOS, osteoporosis with prolonged hypogonadism
- Associated conditions: Metabolic syndrome, insulin resistance, hirsutism, acne, hair loss, menstrual disorders, sexual dysfunction
Follow-up Tests
- Testosterone (total and free): Evaluates androgen excess in women with elevated LH/FSH ratio; assesses hypogonadism in men
- Estradiol: Measures circulating estrogen; important for evaluating ovarian function and postmenopausal status
- Prolactin: Screens for hyperprolactinemia which suppresses gonadotropin secretion and causes hypogonadism
- DHEA-S (Dehydroepiandrosterone sulfate): Assesses adrenal androgen production; elevated in PCOS and adrenal disorders
- 17-Hydroxyprogesterone: Screens for congenital adrenal hyperplasia (CAH), which presents with elevated LH/FSH ratio and hyperandrogenism
- Thyroid function tests (TSH, free T4): Evaluates thyroid contribution to gonadotropin abnormalities
- Fasting glucose and insulin: Assesses insulin resistance common in PCOS; tests for metabolic dysfunction
- Lipid panel: Evaluates cardiovascular risk in PCOS and hypogonadism
- Transvaginal ultrasound: Visualizes ovarian morphology in women; assesses for polycystic ovaries in PCOS
- Semen analysis: Recommended in men with abnormal LH/FSH ratio to evaluate sperm production and motility
- Pelvic imaging (MRI or CT): Indicated when pituitary or adrenal pathology is suspected based on abnormal hormone ratios
- Repeat LH/FSH testing: Recommended in follicular phase for women; may be repeated to confirm diagnosis or monitor treatment response
- Monitoring frequency: PCOS patients monitored every 6-12 months; hypogonadal patients on treatment monitored every 3-6 months initially, then annually
- Additional investigations for infertility: Post-coital test (PCtest), hysterosalpingography (HSG), laparoscopy, and partner evaluation may be warranted
Fasting Required?
- Fasting Required: No
- LH and FSH levels are not significantly affected by food intake; fasting is not required for this test
- Patient may eat and drink normally before blood collection
- Timing recommendations: Blood should be drawn in the morning (7-9 AM) for standardized results due to diurnal variation in hormone secretion
- In women: Test should be performed on cycle day 3, 4, or 5 (early follicular phase) for consistency and accurate interpretation
- Medications to avoid: Hormonal contraceptives should be discontinued 2-3 months prior if possible; hormone replacement therapy (HRT) may affect results
- Medications affecting results: Dopamine agonists (bromocriptine), anticonvulsants, antipsychotics, opioids, and steroids may alter LH and FSH levels
- Special instructions: Patients should avoid strenuous exercise 24 hours before testing; excessive physical activity may temporarily alter hormone levels
- Stress reduction: Minimize stress before testing as psychological stress can affect gonadotropin secretion
- Hydration: Patient should remain well-hydrated; dehydration may affect hormone concentration in blood samples
- Sleep: Adequate sleep (7-9 hours) the night before testing is recommended to minimize cortisol effects on hormone levels
- Documentation: Inform healthcare provider of all current medications, supplements, and recent hormonal treatments before blood draw

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