Luteinizing hormone

Luteinizing hormone (LH, lutropin or lutrophin) is a sex hormone produced by gonadotroph cells in the anterior pituitary gland. 
In females, an LH surge triggers ovulation and development of the corpus luteum (a temporary endocrine structure in female mammals that promotes relatively high levels of progesterone). In males, where LH had also been called interstitial cell–stimulating hormone (ICSH), it stimulates Leydig cell production of testosterone. It acts synergistically with Follicle-stimulating hormone (FSH).
Predicting ovulation.
The detection of a surge in luteinising hormone shows ovulation will soon happen. LH can be detected by urinary test kits. Tests are done daily, round the time ovulation is expected. A swing from a negative to a positive reading suggests that ovulation will occur in 24–48 hours. The women has two days to engage in sexual intercourse or artificial insemination with the intentions of conceiving.
Tests may be read manually using a colour-change paper strip, or digitally with the assistance of reading electronics.