Dr Trevor Howlett
Leicester Royal Infirmary

The pituitary lies under the brain in a bony cavity in the skull. It has a large blood supply and all pituitary hormones leave the gland by blood, thus reaching cells in other parts of the body. The production of pituitary hormones is controlled by messenger substances produced in a specialised area of the brain above the gland - the Hypothalamus. The sole exception to this is the antidiuretic hormone (Vasopressin) which is made in the hypothalamus and released by the posterior pituitary. Vasopressin controls the rate of urine flow.

The hormones produced by the anterior Pituitary gland are: Adrenocorticotrophic Hormone (ACTH) which stimulates the Adrenal glands to produce Cortisol or Hydrocortisone controlling arousal and the response to stress and influencing carbohydrate metabolism; Thyroid stimulating hormone (TSH) which stimulates the Thyroid Gland to produce Thyroxine which controls the metabolism; Luteinising hormone (LH) / follicle stimulating hormone (FSH) act on the ovaries or testes, controlling sexual activity and fertility; Growth hormone (GH) which stimulates protein metabolism and growth and repair of cells; and Prolactin (PRL) which facilitates lactation.

There are many causes of pituitary dysfunction. They include pituitary tumours, surgery or Radiotherapy, tumour lumps near the pituitary, head injury and inflammations or infections. In some cases, there is no apparent cause and in others there is an in-born defect of the brain and pituitary.

The signs and symptoms of pituitary dysfunction vary and depend on which hormones are deficient. Deficiency of ACTH leads to low hydrocortisone causing malaise, tiredness, dizziness and weight loss with a low blood pressure. Deficiency of TSH producing low thyroid hormones causes tiredness, slowness, feeling cold, with weight gain, dry skin and constipation. Deficiency of LH / FSH changes ovarian or testicular function causing low sex drive, no periods or impotence. Deficiency of GH causes Short stature (if it occurs before adult height is obtained), loss of muscle mass and an increase of body fat. Deficiency of vasopressin causes Diabetes Insipidus with production of large quantities of urine, thirst and dehydration. Many hypopituitary people have a reduction of several hormones and thus a mixture of symptoms and signs.

The tests for diagnosing hypopituitarism vary from simple blood tests, for example measuring thyroid function or serum Testosterone, to intermediate tests such as measuring blood cortisol or vasopressin levels. The more complicated tests should be done under the supervision of an Endocrinologist and include the insulin stress test, glucagon test, arginine test or water deprivation test.

The treatment of hypopituitarism, after the cause of pituitary dysfunction has been treated, is long-term and consists of taking replacement hormones. Hydrocortisone can be taken as tablets, either two or three times daily. The daily dose is usually 20-30mg, but it should be increased if the subject has another significant illness. Steroid side effects are only a problem if too much hydrocortisone is taken over a prolonged period. Thyroxine can be taken as tablets. The usual dose of 100-150µg is taken once daily. A blood test to confirm that the dose is correct should be performed every 6-12 months. The Sex hormones Oestrogen and testosterone cannot always be given by tablets. Synthetic oestrogens, usually with Progesterone, can be taken by women as tablets, patches or depot injections. Testosterone is usually given as depot injections or patches. Special techniques are available to help women with hypopituitary dysfunction who wish to become pregnant.

People who are taking long-term treatment for pituitary dysfunction often ask about the possibility that the treatment may bring further health problems or reduce their life expectancy. There is some evidence that heart and circulation problems may be more common than in the general population. The reasons for this are not clear, but suggestions include lack of oestrogen, too much hydrocortisone, too little thyroxine and possibly growth hormone deficiency. Which of the possibilities will eventually be identified as most relevant, we do not know. For the present it is prudent to ensure that sex hormone replacement is adequate and that hydrocortisone and thyroxine dosage is correct. The role of growth hormone is still the subject of clinical trials, but it has been shown to produce symptom improvement in some, but not all, subjects treated.

Smoking, not taking regular exercise, and becoming overweight are much more powerful risk factors in producing heart and circulation problems than those associated with the hormones used in treating hypopituitarism.