Special Precautions/Comments:

Ideally sample should be taken day 2 – 7 of the cycle (follicular phase).

Exogenous oestrogen or testosterone can suppress the hypothalamic-pituitary-gonadal axis and affect interpretation

Additional Information:

Luteinising hormone (LH) is a gonadotrophin secreted from the anterior pituitary in a pulsatile manner in response to secretion of gonadotropin releasing hormone (GnRH) from the hypothalamus. LH works in conjunction with follicular stimulating hormone (FSH) to regulate growth and function of the gonads (ovaries and testes). In females, LH stimulates ovulation and formation of the corpus luteum which secretes progesterone. Progesterone increases the lining of the uterus in preparation for possible oocyte implantation. LH also stimulates the production of androgens, which are eventually converted to estradiol (E2) for follicular development. LH is low in the follicular phase, peaks mid-cycle (ovulation) and decreases in the luteal phase. In males, LH stimulates production of testosterone in Leydig cells. 

LH can be measured alongside FSH and E2 or testosterone to investigate the function of the hypothalamic-pituitary-gonadal axis. Measurement of prolactin and progesterone can also be useful. LH can be measured in the investigation of amenorrhoea, erectile dysfunction, infertility, premature menopause and polycystic ovarian syndrome (PCOS). It may also be measured to assess pituitary function. 

Elevated LH can be seen in primary gonadal failure and in the menopause. In PCOS, an elevated LH:FSH may be seen, but this is not always the case. 

Decreased LH can be seen in hypogonadotrophic hypogonadism which may be caused by a hypothalamic issue (such as GnRH deficiency). It can also be seen in hypopituitarism, where there is no production of 1 or more of the pituitary hormones.  

LH is suppressed in the presence of high levels of oestrogen. This can be seen in pregnancy and in use of exogenous oestrogens, including the oral contraceptive pill and hormone replacement therapy (HRT). Similarly, LH can be suppressed by high levels of testosterone such as in testosterone replacement therapy. Finally, LH can be suppressed by high levels of prolactin (hyperprolactinaemia).