Book 4 - Self Instructional Manual for Cancer Registrars - SEER ...

SECTION JTHE ENDOCRINE SYSTEMThe endocrine system is comprised of ductless glands which manufacture and release specificorganic secretions called hormones directly into the bloodstream to be carded to various parts of thebody where they perform their particular functions. The individual glands are located in widelyseparated parts of the body and form a system only from a functional point of view. In contrast, theexocrine glands, such as the tear, digestive, and sweat glands release their secretions into ductsleading to the body cavities or outside the body as appropriate. (You may wish to review thepancreas, ovary, and testis which are also part of the endocrine system.)The islets of Langerhans of the pancreas are part of the endocrine system and have already beendescribed under the digestive system. The endocrine functions of the ovaries and testes weredescribed under the reproductive system. The remaining endocrine glands and their distinct functionsas well as their interesting relationships with each other are described below.Pituitary Gland (Hypophysis)The pituitary gland (hypophysis) is controlled by the hypothalamus of the brain and links thenervous system to the endocrine system. Located at the base of the brain behind the eyes in the sellaturcica of the sphenoid bone, the pituitary is only the size of a pea. It is referred to as the mastergland since it controls all secretions of hormones within the body. The pituitary gland has two lobes,the anterior lobe (the adenohypophysis) and the posterior lobe of the neurohypophysis). Each lobehas definite functions.The anterior lobe is responsiblefor producing at least the following hormones:• Adrenocorticotrophic hormone: ACTH controls the development and secretoryactivityof the adrenal cortex for secretion of the glucocorticoids (primarily cortisol).• Thyrotrophic (thyroid-stimulating) hormone: TSH stimulates the growth anddevelopment of the thyroid gland and stimulates it to secrete thyroxin and triiodothyronine(together called thyroid hormone).• Follicle-stimulating hormone: FSH stimulates the development of ovarian follicleswhich secrete estrogen in the female. In the male, FSH stimulates the developmentof the seminiferous tubules and promotes spermatogenesis.• Male gonadotrophic hormone (interstitial cell-stimulating hormone): ICSHstimulates the development of the interstitial cells (cells of Leydig) of the testes andthe secretion of testosterone.• Female luteinizing hormone: LH stimulates the secretion of progesterone by thecorpus luteum in the ovaries.• Growth or somatotrophic hormone: GH or STH accelerates growth of bone,muscle, kidney, liver, and adipose tissues.329