Pituitary gland (hypophysis)
The pituitary gland is a small gland located in the middle of the base of the brain. It consists of two parts, the anterior pituitary (adenohypophysis) and the posterior pituitary (neurohypophysis), and is not only connected to but also functionally related to the hypothalamus. These two organs work together and regulate almost all metabolic processes in the body by means of various hormones and other chemical messengers. Many of them have a direct influence on the heart, liver and kidneys, whilst others regulate the hormone production in other glands, e.g. the thyroid.
Since the hypophysis plays a central role in the very complex hormonal feedback loop of the body, it deserves particular consideration from an endocrinological viewpoint. There is hardly a metabolic process in which it is not involved in some way. Here are some examples of hypophysis hormones and their functions.
FSH (Follicle Stimulating hormone)
FSH stimulates the gametes. In women, it stimulates estrogen production in the ovary and the maturation of oocytes. In men, FSH stimulates the production of sperm in the testicular tubules and in the Leydig cells which produce testosterone.
LH (Luteinizing Hormone)
LH also stimulates the gametes. In women, it is responsible for ovulation and the maintenance of the corpus luteum. In men, it stimulates testosterone production and is important in the production of sperm cells.
TSH (Thyroid Stimulating Hormone)
TSH stimulates the thyroid gland to produce two hormones: triiodothyronine (T3) and thyroxine (T4) and regulates thyroid gland function.
ACTH (Adrenocorticotropic Hormone)
ACTH regulates the production of both cortisol and adrenal androgens.
STH (Somatotropic Hormone) / HGH (Human Growth Hormone)
This hormone stimulates body growth, tissues and organs in childhood and adolescence, and is responsible for the maturation and ossification of the skeleton. Since it also influences many body functions in adults, a growth hormone deficiency is treated with growth hormone replacement.
Prolactin is responsible for the development of the mammary glands. During pregnancy it helps in the preparation of the breasts for future milk production. After birth, prolactin promotes the synthesis of milk.