The pituitary gland is a pea-sized structure that is attached by a stalk to the underside of the cerebrum of the brain (see diagram 16.2). It is often called the “master” endocrine gland because it controls many of the other endocrine glands in the body. However, we now know that the pituitary gland is itself controlled by the hypothalamus. This small but vital region of the brain lies just above the pituitary and provides the link between the nervous and endocrine systems. It controls the autonomic nervous system, produces a range of hormones and regulates the secretion of many others from the pituitary gland (see Chapter 7 for more information on the hypothalamus).
The pituitary gland is divided into two parts with different functions - the anterior and posterior pituitary (see diagram 16.3).
Diagram 16.2 - The position of the pituitary gland and hypothalamus
Diagram 16.3 - The anterior and posterior pituitary
The anterior pituitary gland secretes hormones that regulate a wide range of activities in the body. These include:
- Growth hormone that stimulates body growth.
- Prolactin that initiates milk production.
- Follicle stimulating hormone (FSH) that stimulates the development of the follicles of the ovaries. These then secrete oestrogen (see chapter 6).
- melanocyte stimulating hormone (MSH) that causes darkening of skin by producing melanin
- lutenizing hormone (LH) that stimulates ovulation and production of progesterone and testosterone
The posterior pituitary gland
- Antidiuretic Hormone (ADH) or Vasopressin, regulates water loss and increases blood pressure
- Oxytocin, milk "let down"