Hormones

 
Hormones are tiny chemical messengers involved in sending information between various parts of the body. Hormones use the bloodstream as the highway along which they travel to reach different body parts.

Nearly all hormones are released in a pulsatile fashion in short bursts every 1-3 hours. As a result, bloodstream hormone levels can fluctuate over the course of days and weeks.

Estrogen and progesterone are the major female sex hormones, both produced by the ovaries. However, it is the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) that play a role in the mother's ability to conceive. FSH stimulates the ovaries to produce follicles, while LH is critical for ovulation and the production of the corpus luteum. Ovulation is usually ushered in by a drastic peak in LH known as the LH surge.

Another key hormone involved in female reproduction is gonadotropin-releasing hormone (GnRH). Released by the hypothalamus in the brain, GnRH stimulates the pituitary to release FSH and LH. Finally, FSH and LH stimulate the production of sex hormones (testosterone and estrogen) in the testes of men and the ovaries of women, respectively.

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