Drugs that replace, stimulate, or inhibit some of the hormones produced by the pituitary gland
The pituitary gland, located at the base of the brain, produces a number of hormones. These hormones include growth hormone, prolactin, which controls the production of breast milk in women, and vasopressin, which regulates the function of the kidneys.
Drugs for pituitary disorders work in various ways. Some drugs are synthetic hormones that replace missing natural hormones, and others, known as antagonists, reduce the production or action of pituitary hormones.
Drugs that act on the hormones produced directly by the pituitary gland are discussed here. Other drugs whose action on the pituitary gland affects the production of hormones in other parts of the body are discussed elsewhere. These drugs include sex hormones and related drugs, drugs for infertility, corticosteroids, and drugs for labour.
A number of drugs are used to treat pituitary disorders. Growth hormone and growth hormone antagonists are given to adjust levels of growth hormone that are either too low or too high. Prolactin inhibitors are given to reduce levels of prolactin in the treatment of disorders in which there is excessive production of prolactin by the pituitary gland. The pituitary disorder diabetes insipidus, which results from insufficient vasopressin, is treated by replacement of the hormone with a synthetic equivalent.
If the pituitary gland does not secrete sufficient growth hormone during childhood, a synthetic form of the growth hormone can be prescribed to replace it. Low levels of growth hormone in childhood can cause impaired growth (see Growth disorders). If a child begins the treatment at an early age, well before puberty, normal growth usually takes place. The drug is usually administered daily by injection. This treatment normally continues for several years until the child reaches adult height. Side effects may include aching muscles and joints and headaches.
If too much growth hormone is produced by the pituitary gland, adults may be given growth hormone antagonists such as octreotide. Excess growth hormone can cause abnormal enlargement of certain parts of the body, particularly facial features, hands, and feet, a condition that is known as acromegaly. In adults, overproduction of growth hormone is most commonly caused by a pituitary tumour. Drugs that block the production of growth hormone may be prescribed as a temporary measure prior to surgery or radiotherapy. However, where surgery is not possible, these drugs may be given long term.
The drugs octreotide and lanreotide are given by injection. Bromocriptine is taken orally. Possible side effects of octreotide and lanreotide include diarrhoea and cramping abdominal pain. Bromocriptine may cause nausea, vomiting, constipation, headache, drowsiness, confusion, nasal congestion, and hallucinations. It has also been associated with abdominal, heart, and lung problems, and your doctor may therefore monitor you regularly.
These drugs are used to suppress production by the pituitary gland of the hormone prolactin, to treat conditions such as noncancerous pituitary tumours (see Prolactinoma). The drugs may also be used to suppress milk production after childbirth and to treat Parkinson’s disease. Prolactin inhibitors are most commonly taken orally. The drugs may cause a wide range of side effects, including nausea, vomiting, constipation, headache, drowsiness, confusion, nasal congestion, and hallucinations. They have also been associated with certain abdominal, lung, and heart problems, and people taking these drugs may therefore be monitored regularly by their doctor.
You may be given vasopressin or a synthetic form of this hormone (desmopressin) if you have cranial diabetes insipidus. In this disorder, the pituitary gland produces insufficient vasopressin to regulate kidney function, which controls the amount of water retained in the body. It may be given orally, as a nasal spray, or by injection.
Vasopressin or desmopressin may cause some side effects, including nausea, belching, and abdominal cramps.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.