LH is released by the pituitary and instructs the gonads to make sex steroids: testosterone from the testicular Leydig cells, and in women the mid-cycle surge that triggers ovulation and sustains the corpus luteum. The test reports on the pituitary end of the reproductive axis. It is read as a control signal, not as a hormone with direct tissue effects.
No readings for this marker yet.
Raised LH most often points at reduced gonadal output, with the pituitary compensating, as in primary testicular failure, ovarian insufficiency or menopause; in women a persistently raised ratio to FSH is also seen in polycystic ovary syndrome. Lowered LH more often indicates that the pituitary or hypothalamus is under-signalling, which occurs with pituitary disease, high prolactin, illness, heavy training, weight loss or exogenous testosterone. The same value can be normal or clearly abnormal depending on the sex hormone measured with it. Interpretation belongs with a doctor, and one result is rarely enough.
LH is secreted in pulses, so consecutive samples differ, and in women the result is meaningless without the cycle day, since the ovulatory surge is many times the baseline. Stress, acute illness and hormonal contraception shift it. It is read with FSH and with testosterone or estradiol, and with prolactin when both gonadotropins are low.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.