Overview.
Most fertility challenges have measurable hormonal signatures that appear well before months of unsuccessful attempts. A targeted blood panel can identify problems with ovarian reserve, ovulation quality, thyroid function, insulin sensitivity, and androgen excess — each responding to different interventions. Acting on these earlier changes outcomes. The ASRM recommends systematic, expeditious evaluation beginning with the least invasive but highest-yield investigations. For men, the AUA/ASRM 2024 guideline reinforces that hormonal and semen analysis evaluation should run in parallel with female assessment, not sequentially.
Ranked biomarkers.
#1 AMH (Anti-Müllerian Hormone)
AMH directly reflects the number of remaining ovarian follicles. It can be measured on any cycle day, making it the most practical reserve marker. Low AMH predicts poor IVF response and a shorter reproductive window. The 2023 PCOS guideline now validates AMH as a diagnostic surrogate for polycystic ovarian morphology.
Optimal range: 1.5-4.0 ng/mL (fertility); <1.0 = diminished reserve; >3.4 + hyperandrogenism = PCOS
Key insight: AMH does not predict natural conception rates in regularly ovulating women. Its value is predicting ovarian stimulation response and estimating reproductive aging timeline — not whether a single egg each cycle will be fertilised.
#2 FSH (Follicle-Stimulating Hormone)
Elevated Day 3 FSH (>10 mIU/mL) signals diminished ovarian reserve — the pituitary compensating for weakened ovarian response. In men, elevated FSH is the biochemical hallmark of primary testicular failure. The 2024 POI guideline uses FSH >25 mIU/mL as a diagnostic criterion.
Optimal range: Women Day 3: <8 mIU/mL (reassuring); Men: 1.5-12.4 mIU/mL
Key insight: FSH and AMH carry complementary but non-redundant information. A woman can have normal FSH but low AMH, indicating early reserve decline that FSH hasn't caught yet. Both should always be measured together.
#3 Total Testosterone
In men, intratesticular testosterone drives spermatogenesis; low levels impair sperm production and libido. In women, excess testosterone is the defining biochemical feature of PCOS hyperandrogenism, causing anovulation. Critically, exogenous TRT suppresses spermatogenesis within weeks.
Optimal range: Men: 300-1000 ng/dL (morning draw); Women: 15-70 ng/dL (>60-70 = hyperandrogenism)
Key insight: Men on TRT who want children must switch to gonadotropin therapy (FSH + hCG). TRT shuts down spermatogenesis through negative feedback on FSH/LH. Recovery after stopping can take 12-24 months.
#4 TSH (Thyroid-Stimulating Hormone)
Both overt and subclinical hypothyroidism cause menstrual irregularity, anovulation, elevated prolactin, and increased miscarriage risk. A 2024 meta-analysis found levothyroxine treatment in subclinical hypothyroidism improved pregnancy rates and reduced miscarriage, especially in women undergoing ART.
Optimal range: Fertility-specific: <2.5 mIU/L for IVF (ASRM 2024); <4.0 mIU/L for natural conception
Key insight: TPO antibodies should be measured alongside TSH. Women who are TPO-positive have higher miscarriage rates even when TSH is within normal range. This is often missed on standard fertility panels.
#5 Progesterone (Mid-Luteal)
The definitive ovulation confirmation test. Without ovulation, there is no corpus luteum and no progesterone rise. Sub-optimal mid-luteal progesterone is associated with impaired implantation. In IVF frozen embryo transfer, lower progesterone on transfer day significantly reduces pregnancy and live birth rates.
Optimal range: >3 ng/mL confirms ovulation; >10 ng/mL = well-functioning corpus luteum
Key insight: Low progesterone in women with regular cycles doesn't necessarily mean 'luteal phase defect' — it more often reflects poor follicular development upstream. Treating the root cause (optimising ovulation) is more effective than progesterone supplementation alone in natural cycles.
#6 Fasting Insulin / HOMA-IR
Insulin resistance is the metabolic driver behind many cases of anovulatory PCOS — present in 50-80% of women with PCOS regardless of BMI. Insulin sensitisation with inositol or metformin improves ovulation rates, menstrual regularity, and hormonal profiles. In men, insulin resistance impairs sperm motility.
Optimal range: HOMA-IR <2.0 (normal); >2.5-3.0 = clinically relevant resistance
Key insight: HOMA-IR is not on standard fertility panels — you must specifically request fasting insulin alongside fasting glucose. In lean PCOS women, insulin resistance may be 'metabolically hidden' yet still functionally impair ovarian response to FSH.
#7 LH (Luteinizing Hormone)
The biological ovulation trigger. Day 3 LH:FSH ratio >2:1 is a key PCOS indicator reflecting disrupted follicular recruitment. In men, the LH level distinguishes primary from secondary hypogonadism — which determines the entire treatment pathway.
Optimal range: Women follicular: 2-15 mIU/mL; LH:FSH <2:1; Men: 1.7-8.6 mIU/mL
Key insight: At-home ovulation kits detect LH surges but cannot distinguish a normal surge from the persistently elevated tonic LH in PCOS. Women with PCOS who get positive OPKs may not be ovulating normally — with real implications for natural conception timing.
#8 Prolactin
Elevated prolactin suppresses GnRH pulsatility, reducing FSH/LH and causing anovulation or amenorrhoea. It accounts for 15-20% of female infertility cases. Dopamine agonists (cabergoline) normalise prolactin and restore fertility in the majority of patients — making this one of the most treatable causes.
Optimal range: Women: <25 ng/mL; Men: <20 ng/mL. >200 ng/mL = almost always prolactinoma
Key insight: Stress, exercise, food, and even the stress of the blood draw can transiently elevate prolactin. A single elevated result should always be repeated fasting and relaxed. Also ask about macroprolactinaemia (biologically inactive form) — it affects up to 25% of apparent hyperprolactinaemia cases.
#9 Vitamin D (25-OH)
Vitamin D receptors are present in ovaries, endometrium, testes, and sperm. Deficiency is associated with increased miscarriage risk, and supplementation in women with PCOS improves ovulation rates and pregnancy rates. In men, supplementation improves sperm parameters.
Optimal range: >30 ng/mL (sufficient); target 40-50 ng/mL for fertility
Key insight: Vitamin D deficiency is not fertility-specific — it's systemic with downstream reproductive effects. Supplementation is low-cost, low-risk, and broadly beneficial, making it one of the few evidence-based preconceptual interventions where the risk-benefit calculation strongly favours action.
#10 Estradiol (E2)
Day 3 estradiol above 60-80 pg/mL can mask diminished ovarian reserve by suppressing FSH via negative feedback — the 'high E2, normal FSH' confounder. In men, excess estradiol (common in obesity) suppresses the HPG axis and impairs sperm production.
Optimal range: Women Day 3: <60-80 pg/mL; Men: 10-40 pg/mL
Key insight: A high Day 3 estradiol is one of the most common reasons for IVF cycle cancellation — the ovary has already recruited a dominant follicle before Day 3, indicating a shortened follicular phase and typically poorer egg quality. Always measure E2 alongside FSH to avoid false reassurance.
How to test.
Women: Request a Day 2-5 fertility panel (FSH, LH, estradiol, AMH, TSH + TPO antibodies, prolactin, fasting insulin + glucose, vitamin D). Add testosterone if PCOS suspected. Progesterone requires a separate Day 21 draw. Men: Same-day morning fasting hormonal panel (testosterone, FSH, LH, prolactin, estradiol, vitamin D, fasting insulin) alongside a semen analysis. Both partners should be evaluated in parallel — delaying male evaluation wastes months.
FAQs.
Can I test these biomarkers at home without a doctor?
Many markers are available through direct-to-consumer labs (Quest, LabCorp, Medichecks). AMH, TSH, and basic fertility hormones are widely available. However, interpretation of borderline results — especially cycle-timed hormones — should involve a healthcare provider familiar with reproductive medicine.
My AMH is low — does that mean I can't get pregnant naturally?
No. Low AMH predicts poor IVF response, not impossibility of natural conception. Women with low AMH who ovulate regularly can and do conceive. But low AMH signals that time is a factor — the window may be narrower, so don't delay evaluation.
What TSH level is right for trying to conceive?
The ASRM 2024 guideline recommends TSH <2.5 mIU/L for women undergoing IVF and <4.0 mIU/L for natural conception. If above these thresholds, discuss low-dose levothyroxine with your provider, particularly if you also have elevated TPO antibodies.
Do these biomarkers change over time? Should I retest?
Yes. AMH declines with age, FSH rises as reserve declines, vitamin D fluctuates seasonally, and TSH shifts with stress or disease. Repeat panels annually while actively trying, or sooner after new diagnoses, weight changes, or treatment interventions.
Verdict.
These 10 biomarkers cover the major actionable dimensions of reproductive biology: ovarian reserve (AMH, FSH, estradiol), ovulation quality (LH, progesterone, prolactin), androgen status (testosterone), thyroid function (TSH), metabolic health (insulin/HOMA-IR), and micronutrient support (vitamin D). Each is measurable, and most abnormalities have evidence-based interventions. The ideal fertility panel is not a single test ordered once — it's a structured, cycle-timed assessment that maps the system together.