Endocrines or hormones are the substances produced by various glands, which are carried by blood or other body fluids to influence and control the pigs metabolism. There are nine main glands (Fig.1-4) in the pig which are responsible for controlling a variety of vital functions.

Generally the diseases associated with the failure of the endocrine glands are not important in the pig. However when the regulatory and stimulatory mechanisms between the hypothalamus, the anterior pituitary gland and the ovaries fail, anoestrus (not coming on heat) or reproductive malfunction result, including cystic ovaries. In the male testicular function is affected. The hypothalamus stimulates the anterior part of the pituitary gland to release the follicle stimulating and luteinising hormones (FSH and LH). These in turn act upon the ovaries and the testes to regulate their function. (See chapter 5).

Terminology
Follicle stimulating hormone (FSH) - Produced by the anterior pituitary gland. It stimulates the formation of follicles in the ovaries,
Growth hormone - Responsible for promoting growth of most tissues throughout the body. It is produced by the pituitary gland in association with the hypothalamus.
Hypothalamus - An area in the brain responsible for providing both nervous and hormonal control over most other hormone producing glands.
Luteinising hormone (LH) - Stimulates ovulation and is produced by the pituitary gland.
Oestrogen - The female hormone responsible for all the female sexual characteristics. It is produced by the ovary.
Oxytocin - Produced by the pituitary gland. This stimulates uterine contractions during farrowing and causes milk let down. It also aids in the movement of sperms and eggs.
Progesterone - The hormone that maintains pregnancy. It is produced by the corpus luteum in the ovary.
Prolactin - This is produced by the pituitary gland and controls milk production.
Prostaglandins - These are produced by the uterus and the placenta and are associated with the initiation of farrowing or abortion.
Testosterone - The male hormone responsible for all the male sexual characteristics. It also controls the development of sperm.