LUTEINISING HORMONE (LH) - serum

---

Specimen: 5 mL blood in plain tube.

Method: Immunoassay.

Reference Interval: Levels will be dependent on the method used, the age and gender of the patient, and in females, the stage of the menstrual cycle and whether the patient is post-menopausal. LH secretion is pulsatile and single results may be misleading.

Adult male:	2-10 U/L
Adult female:	2-15 U/L
Post-menopausal:	15-100 U/L

Application: Investigation of male and female infertility, to distinguish primary gonadal failure from pituitary/hypothalamic failure. Identification of ovulation in the investigation of menstrual cycle disturbances and female infertility. Suspected LH secreting pituitary tumour.

Interpretation: High levels are found in primary gonadal failure. Low levels occur with hypothalamic failure (responds to gonadotrophin releasing hormone) and pituitary failure (no response). LH peak occurs just prior to, and identifies, ovulation. Polycystic ovary syndrome is associated with an increased LH/FSH ratio. If amenorrhoea is due to undiagnosed pregnancy, spuriously elevated results may be obtained using older assay methods which show cross reactivity with hCG. Interpretation of LH levels and LH responses to gonadotrophin releasing hormone is often difficult - consult pathologist.

Reference: Thorner MO et al and Carr BR. In: Wilson JD and Foster DW eds. Williams Textbook of Endocrinology. 8th ed. WB Saunders 1992.

---