Dr Colin Dayan
University of Bristol

Hypopituitarism is the failure of the Pituitary gland to produce sufficient amounts of one or more of the pituitary hormones. The pituitary produces six hormones from the anterior (front) pituitary and two from the posterior (back) pituitary, all of which control the activity of other glands in the body.

The anterior pituitary produces Adrenocorticotrophic Hormone (ACTH), which controls the production of Cortisol from the Adrenal glands. Thyroid stimulating hormone (TSH) controls the production of triiodothyronine (T3) and Thyroxine (T4) by the Thyroid Gland. Luteinising hormone (LH) and follicle stimulating hormone (FSH) are Gonadotrophins that control Oestrogen production by the ovaries in women. In men LH controls Testosterone production by the testicles. Prolactin controls milk production in the breast and Growth hormone (GH) acts on the liver to produce Insulin-like Growth Factor-1 (IGF-1).

The posterior pituitary produces Anti-diuretic Hormone (ADH), which acts on the kidneys to control the water balance within the body, and oxytocin, which acts on the breasts and enables the release of milk in response to babies' suckling.

There are five main causes of hypopituitarism:

• Incomplete development of the pituitary in children. This commonly affects GH production. It is unusual for production of all pituitary hormones to be affected.
• A pituitary or brain tumour. The tumour squashes the pituitary and causes production of too much or little of a hormone. Squashing usually occurs very gradually but may happen suddenly and cause pituitary Apoplexy, characterised by severe headaches and blindness. Prompt surgery can restore sight.
• Surgery. Removal of a lump from the pituitary can cause damage.
• Radiotherapy. Treating a Pituitary tumour can damage the healthy pituitary slowly over months or years, even after a short period of treatment.
• Sheehan's syndrome. This is a condition caused by a sudden drop in blood pressure after childbirth, causing a lack of prolactin and inability to breast-feed the baby.

Deficient hormones and their effects

ACTH - tiredness, failure to grow and collapsing in adults and children, especially under stress.

TSH - anaemia and failure to grow in children, tiredness, weight gain, dry skin and slow pulse rate in adults.

LH and FSH - neither girls nor boys enter puberty or have a normal growth spurt. Women experience infertility, a lack periods, decreased sex drive and Osteoporosis. Men experience impotence, lack of sex drive and osteoporosis.

GH - is important for growth between the ages of 1 year and puberty. Adult symptoms include tiredness, weight gain and weak muscles. Too much GH is associated with a higher risk of tumour growth.

Prolactin - no effects are recorded with children or men but women lack breast milk.

How are hormones replaced?

In general, the hormones controlled by the pituitary gland, not the pituitary hormones themselves, are replaced. This is because pituitary hormones would have to be replaced by injection, unlike the replacement hormones that can usually be taken in tablet form. Cortisol tablets are taken two to three times a day and thyroxine once a day.

Women lacking LH and FSH are treated by hormone replacement therapy (HRT), whereby oestrogen is taken in the form of tablets, patches on the skin or pellet implants under the skin. Women who have not undergone the menopause or have not had a hysterectomy must also take Progesterone tablets, as 'unopposed' oestrogens can cause cancer of the uterus. Men lacking LH are given intramuscular injections of testosterone two to four times weekly, patches daily or implants. Oestrogen and testosterone replacement will not make patients fertile. Women require regular injections of LH and to cause the release of eggs from the ovaries, and men require 3 to 6 months of daily LH injections to become fertile, at which point sperm may also be frozen.

GH is the one pituitary hormone that must be given directly by daily injection, usually at night when GH would naturally be produced.

Prolactin is not replaced in any form.