Small as a hazelnut, huge in effect: the pituitary gland (hypophysis) controls a wide variety of functions in the body through hormones – from body growth to milk production after childbirth to urinary excretion. Learn more about the control center of our hormonal system here.
What does the pituitary gland look like and where exactly is it located?
The Greek name pituitary gland literally means “the plant attached below.” That describes its anatomical position pretty well: the pituitary gland “hangs below” our brain. It sits on the sella turcica (Turk’s saddle), a depression in the base of the skull in the middle of our skull, at about the level of the nose and ears. It is just under one centimeter in size and about one gram in weight.
The pituitary gland consists of the anterior pituitary lobe (HVL, adenohypophysis) and the posterior pituitary lobe (HHL, neurohypophysis). The region between the two lobes is called the pars intermedia. Via the pituitary stalk, the pituitary gland is connected to the hypothalamus, a part of the diencephalon.
The neurohypophysis is a part of the brain, namely an outpouching of the diencephalon. The adenohypophysis is a hormonal gland. Together, the hypothalamus and pituitary gland form an important functional unit.
What is the function of the pituitary gland?
The anterior pituitary gland produces hormones, and the posterior pituitary gland is a storage site for hormones produced by the hypothalamus. The pars intermedia is functionally part of the HVL, as it also produces a hormone.
What happens in the anterior pituitary lobe?
The adenohypophysis makes the following hormones:
- Adrenocortical stimulating (adrenocorticotropic) hormone (ACTH).
- The growth hormone (also: growth hormone = GH or somatotropin = STH).
- The thyroid stimulating hormone (TSH).
- The follicle stimulating hormone (FSH)
- The luteinizing hormone (LH)
- Prolactin
ACTH stimulates the adrenal glands to produce cortisone, aldosterone and androgens.
GH respectively STH promotes growth by providing energy: Liver and adipose tissue release fats and sugars. The liver also stimulates bone growth. In addition, GH promotes protein formation.
TSH acts on the thyroid gland, causing it to produce more hormones.
FSH and LH stimulate the production of sex hormones in the testes and ovaries, respectively. In women, they cause the eggs to mature and trigger ovulation; in men, they are responsible for sperm formation.
Prolactin promotes the growth of the mammary gland and milk production, while at the same time inhibiting ovulation. However, this natural form of “contraception” in nursing mothers should not be relied on exclusively.
The activity of the adenohypophysis is controlled by the hypothalamus, which releases “control hormones”: Inhibiting hormones slow down production, releasing hormones promote it. “Feedback” from the respective target organs also influences the function of the HVL.
What happens in the posterior pituitary lobe?
The HHL is made up of nerve cells whose heads are located in the hypothalamus, which is why it is also called the neurohypophysis. It serves as a storage site for two hormones that are produced in the hypothalamus and enter the posterior pituitary via the nerve cells:
Antidiuretic hormone (ADH, also vasopressin or adiuretin) acts on water reabsorption in the kidneys. Urinary excretion decreases and water is retained in the body. Urine is more concentrated, which can be noticed by color and odor. In addition, ADH can constrict blood vessels and increase blood pressure.
Oxytocin triggers labor in pregnant women by causing the muscles of the uterus to contract. In addition, it provides “milk let-down” after birth.
What does the pars intermedia do?
The pars intermedia produces melanocyte-stimulating hormone (MSH, melanotropin). MSH stimulates the production of melanin in our skin pigment cells (melanocytes), which protects us from the sun’s harmful UV rays. In addition, MSH controls our appetite and sexual arousal.
