Reproductive, Fertility & Pregnancy Labs

Solve the Vermeulen equation for free testosterone from total testosterone, SHBG and albumin — the calculation validated against equilibrium dialysis.

Convert oestradiol between pg/mL, pmol/L and ng/L, and see why a single value means nothing without the day of the cycle.

Calculate the free androgen index from total testosterone and SHBG, a simple but crude surrogate used mainly in the assessment of women.

mIU/mL, IU/L and mU/mL are the same number for FSH — this page confirms that and then does the part that matters, the reference intervals.

Calculate the doubling time from two hCG results and the hours between them, and see how far it can and cannot take an early-pregnancy assessment.

mIU/mL, IU/L and mU/mL are the same number for hCG — the useful part of this page is the discriminatory zone, the doubling rule and the hook effect.

Calculate the LH to FSH ratio and see why a value above 2 is a classic feature of PCOS but not, on its own, a diagnostic one.

Convert progesterone between ng/mL, nmol/L and µg/L, with the mid-luteal thresholds for ovulation and why pulsatile release blunts a single value.

Convert prolactin between µg/L, ng/mL and mIU/L at 21.2 mIU/L per µg/L — then check for macroprolactin and the hook effect, which change what the number means.

Classify a semen analysis against the WHO 2021 sixth-edition lower reference limits — and see why those limits are not fertility thresholds.

Calculate the angiogenic ratio used to rule out pre-eclampsia within one week, and see how the rule-in threshold changes with gestation.

Convert testosterone between ng/dL, ng/mL and nmol/L, with sex-specific ranges and why the time of sampling changes the answer.