Chemical substances manufactured by the endocrine glands and secreted directly into the bloodstream. As the heart pumps blood through the body they are borne to cells remote from their point of origin where they have a specific effect. Hormones are to physiology what radium is to chemistry.
These are ‘chemical messengers’ that are dispersed by the blood and act on target organs to produce effects distant from their point of release. The main organs involved in hormone production are the PITUITARY GLAND, PANCREAS, ovary (see OVARIES), testis (see TESTICLE), THYROID GLAND, and ADRENAL GLANDS. The release of many hormones is, ultimately, under the control of the central nervous system via a series of inhibiting and releasing factors from the HYPOTHALAMUS. Hormones are involved in maintaining homeostasis: for example, insulin regulates the concentration of glucose in the blood. They also participate in growth and maturation: for example, growth hormone promotes growth and helps to regulate fat, carbohydrate, and protein metabolism; and the sex hormones promote sexual maturation and reproduction. (See also ENDOCRINE GLANDS.)
These HORMONES control the development of primary and secondary sexual characteristics. They also regulate sex-related functions – for example, menstruation and the production of sperm and eggs. The three main types of sex hormone are androgens, or male sex hormones (see ANDROGEN); OESTROGENS, or female sex hormones; and progesterones, which are involved in pregnancy (see PROGESTERONE).... sex hormones
A group of hormones released from specialized cells in the stomach, pancreas, and intestine that control various functions of the digestive organs. Gastrin, secretin, and cholecystokinin are the best known of these hormones.... gastrointestinal hormones
Hormones that stimulate cell activity in the ovaries and testes. Gonadotrophins are essential for fertility. The two most important gonadotrophins are follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are secreted by the pituitary gland. Another gonadotrophin, HCG (see gonadotrophin, human chorionic), is produced by the placenta during pregnancy. Certain gonadotrophins are used as drugs in the treatment of infertility.... gonadotrophin hormones
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