Professor Jayne Franklyn
University of Birmingham

The Pituitary gland is the most important endocrine gland in the body, as it produces several important hormones. In turn, these hormones control most of the other hormone systems in the body. The hormones produced by the anterior pituitary include Growth hormone (GH), Thyroid stimulating hormone (TSH), adrenal stimulating hormone (also known as Adrenocorticotrophic Hormone or ACTH), Luteinising hormone (LH) and follicle stimulating hormone (FSH) (also known as the gonad stimulating hormones or Gonadotrophins) and Prolactin (Prl). The posterior pituitary produces a hormone called Vasopressin (also known as Anti-diuretic Hormone or ADH).

The most common causes of hypopituitarism are tumours of, or close to, the pituitary. The vast majority of these tumours are non-functional i.e. the tumour itself does not produce any hormones, but tumours also occur that overproduce one of the other hormones produced by the pituitary e.g. Prolactinoma. If these tumours compress and damage the normal pituitary tissue, the pituitary can no longer function normally and this results in deficiency of the pituitary hormones (hypopituitarism). The term panhypopituitarism refers to deficiency of all the pituitary hormones. Other causes of hypopituitarism include trauma (usually caused by a significant head injury), Radiotherapy, pituitary infarction and very rare diseases or infections such as sarcodosis.

Most of the pituitary hormones are tiny little molecules, which are rapidly broken down by the body. As a result of this, they cannot be taken orally as they would be digested within minutes by the enzymes in the gut. Replacement of the pituitary hormones themselves could only be given by repeated injection during the course of the day. It is much more natural and physiological to replace the hormone that would be produced by the target gland, which is why pituitary deficiency is dealt with by giving the target hormone instead.

Growth hormone itself is not what makes us grow. GH acts principally on the liver to produce growth factors, the most important of which is called Insulin-like Growth Factor-1 (IGF-1). These growth factors then stimulate bone and cartilage production in children to make them grow before the growth plates in their bones have fused. Consequently, GH deficiency in children results in Short stature and failure to grow. When GH treatment is initiated for GH deficient, children the children usually have a good long-term outlook in terms of achieving a normal adult height. GH has to be given for many years and can only be given by injection, usually on a daily basis. The effects of growth hormone deficiency in adulthood are less severe than the effects of deficiencies of other pituitary hormones. It has therefore taken more time to establish the value of growth hormone replacement in adults.

In women, the gonadotrophins are responsible for stimulating the ovaries and the production of Oestrogen and Progesterone. Symptoms of deficiency in these hormones include poor libido and typical menopausal type symptoms (symptoms of oestrogen deficiency). Gonadotrophin deficiency is treated using a combination of oestrogen and progesterone e.g. HRT. In men, the gonadotrophins are responsible for the production of Testosterone and thus, for the male secondary sexual characteristics. Consequently, the symptoms of gonadotrophin deficiency include poor libido and a reduction in body hair and muscle bulk. Testosterone replacement is usually administered by injection, but can also be taken orally, as a patch on the skin or by implants. Lack of the gonadotrophins (Hypogonadism) can affect the fertility of both sexes.

A lack of TSH results in deficiency of the thyroid hormones, Thyroxine (T4) and triiodothyronine (T3). Symptoms of thyroxine deficiency include lack of energy, feelings of coldness, dryness of the skin and hair, weight gain, constipation, a gruff voice, aches and pains, a puffy face, bradycardia (slow heartrate) and mood disturbances. Thyroxine replacement is not a treatment that requires a great deal of fine-tuning.

A lack of ACTH results in deficiency of the steroids from your Adrenal glands. The symptoms associated with a lack of steroid hormones can be quite non-specific i.e. tiredness, weariness, faintness. One of the features of ACTH deficiency is paleness of the skin as ACTH is partly responsible for our skin colour. To mimic the normal production of Cortisol, Hydrocortisone is typically given in two doses, one in the morning and a second in the evening.

Vasopressin (ADH) acts on the kidneys to control the water balance in the body. Deficiency in ADH results in a condition called Diabetes Insipidus (DI) where the kidneys cannot concentrate the urine. DI can occur as a result of a Pituitary tumour, head injury or sometimes following pituitary surgery, especially in the early weeks or months. DI is relatively easy to treat by replacing the ADH, in milder cases by tablets and otherwise by spray or sometimes by injection.