Hormones and Endocrine System

Endocrine disorders, usually resulting in too much or too little of a particular hormone, have a variety of causes. Some are congenital in origin; others may be caused by cancer, autoimmune disease (including some forms of diabetes mellitus), injury, and certain medicaments.

Natural hormone preparations or their synthetic versions are often prescribed to treat deficiency. Sometimes medicaments are given to stimulate increased hormone production in the endocrine gland, such as oral antidiabetic medicaments. When too much hormone is produced, medicament treatment may reduce the activity of the gland.

Hormones or related medicaments are also used to treat other conditions. Corticosteroids are related to adrenal hormones, and are used to relieve inflammation and to suppress immune system activity. Several types of cancer are treated with sex hormones. Female sex hormones are given as contraceptives and to treat menstrual disorders.

Corticosteroids

The adrenal glands, atop each kidney, produce hormones that regulate a variety of body functions. One important group of hormones produced in the outer part of each adrenal gland (cortex) is the corticosteroids. Release of these hormones is governed by the pituitary gland. Corticosteroids have two types of effect: glucocorticoid and mineralocorticoid. The glucocorticoid effects include the maintenance of normal levels of sugar in the blood and the promotion of recovery from injury and stress. The main mineralocorticoid effect is the regulation of the balance of mineral salts and the water content of the body. When present in large amounts, corticosteroids reduce inflammation and suppress allergic reactions and immune system activity.

Corticosteroid medicaments -often referred to simply as steroids -are derived from or are synthetic variants of the natural corticosteroid hormones. They are distinct from another group of hormones, the anabolic steroids.

Although corticosteroids have broadly similar actions, they vary in their relative strength and duration of action. The strength of mineralocorticoid effects also varies.

Given in high doses, corticosteroid medicaments reduce inflammation by blocking the action of chemicals called prostaglandins that are responsible for triggering the inflammatory response. They also temporarily depress the immune system by reducing the activity of certain types of white blood cells.

Corticosteroid medicaments often produce a dramatic improvement in symptoms. Given systemically, corticosteroids may also act on the brain to produce a heightened sense of well-being and, in some people, a sense of euphoria.

Troublesome day-to-day side effects are rare. However, long-term, high-dose corticosteroid treatment carries a number of serious risks. Few risks are associated with these medicaments when they are given in low doses by mouth for the treatment of Addison's disease. Expected adverse effects from higher doses depend on the medicament used and the duration of treatment.

Medicaments with strong mineralocorticoid effects such as hydrocortisone may cause water retention, swelling (particularly of the ankles), and an increase in blood pressure. Because corticosteroids reduce the effect of insulin they create problems in diabetics. They may even give rise to diabetes in susceptible individuals. They can also contribute to peptic ulcers.

Since corticosteroids suppress the immune system, they increase susceptibility to infection. They also suppress symptoms of infectious disease. With long-term use, corticosteroids may cause a variety of adverse effects. Physicians try to avoid long-term prescription of corticosteroids to children because prolonged use may retard growth.

Long-term use of corticosteroids suppresses the production of the body's own corticosteroid hormones. For this reason, treatment lasting for more than a few weeks should be withdrawn gradually to give the body time to adjust. If the medicament is stopped abruptly, the lack of corticosteroid hormones may lead to sudden collapse. People taking corticosteroids by mouth for longer than one month are advised to carry a warning card for two years. In the case of an accident, their defenses against shock may need to be quickly strengthened with extra hydrocortisone.

Medicaments used in diabetes

The body obtains most of its energy from glucose, a simple form of sugar broken down in the intestine from starch and other sugars and absorbed into the bloodstream. The hormone insulin, produced by the pancreas, enables body tissues to take up glucose from the blood, either to use it for energy or store it. In diabetes mellitus (also called sugar diabetes) not enough insulin is produced by the pancreas, so that little glucose is taken up by the tissues and glucose in the blood rises to abnormal levels, a condition known as hyperglycemia.

There are two main types of diabetes mellitus. Insulin-dependent, or type 1, diabetes, the most severe form, usually first appears in people under 35 and, commonly between the ages of 10 and 16. It develops rapidly when insulin secreting cells in the pancreas are destroyed, probably as a result of antibodies attacking the pancreas, possibly triggered by a virus. Insulin production ceases, often rapidly, leading to symptoms of hyperglycemia: lethargy, general ill health, weight loss, thirst, and increased urination. If treatment is not given, coma and death may result.

The other main form of the disorder, non -insulin-dependent, maturity -onset, or type 2 diabetes, is usually of gradual onset and occurs mainly in people over 40. Insulin is produced, but not in sufficient amounts to meet the body's needs. It is especially common among overweight people who eat large amounts of sugary foods. This form of diabetes may also be caused by chronic pancreatitis and may occasionally be triggered by medicaments such as oral contraceptives or corticosteroids.

In both types of diabetes it is necessary to change the diet to reduce consumption of sugary foods. For many obese type 2 diabetics, control of sugar intake and loss of excess weight reduce the body's insulin requirements to a sufficiently low level without the need for further treatment. However, many type 2 diabetics and all type 1 diabetics require some form of medicament treatment in addition to those simpler measures. Two types of medicament can be used -insulin and oral antidiabetic medicaments, the sulfonylureas and metformin.

Sulfonylurea oral antidiabetic medicaments encourage the pancreas to release insulin and allow the insulin to work better in the cells. They are therefore effective only when some insulin-secreting cells remain active. Insulin injection directly replaces the natural hormone that is deficient in diabetes mellitus.

By increasing insulin levels in the blood, both types of medicament promote the uptake of glucose into body tissues and help to prevent an excessive rise in the level of glucose in the blood. Insulin cannot be given by mouth because it is broken down in the digestive tract before it reaches the blood- stream. Regular injections are therefore necessary.

Antidiabetic medicaments rapidly relieve symptoms of diabetes and, in combination with dietary measures, usually permit a diabetic to lead a full and healthy life. Successful control of blood glucose levels helps to reduce the long-term risks of diabetes mellitus.

Because the body's requirement for glucose and therefore for insulin varies according to the level of activity and the rate at which the body burns up energy, the main day-to-day problems arise out of the difficulty in establishing a dosage and schedule to meet individual variations. Symptoms of hyperglycemia may develop if the dose is too low, and those of hypoglycemia (low blood glucose) may arise if the dose is too high. The warning symptoms of hypoglycemia include sweating, dizziness, and faintness.

Insulin regimens are tailored to each individual's particular needs. Dosage is established for a particular calorie intake and exercise level, making it important to maintain regular eating habits and levels of activity.

Insulin was traditionally extracted from the pancreases of pigs and cattle. Animal insulin may, however, cause allergic reactions in some people. A skin rash at the injection site develops, along with reduced effectiveness of the medicament. A human insulin, produced by genetic engineering or by modifying pork insulin, is now available and is prescribed instead. Repeated injection at the same site may disturb the fat layer beneath the skin, producing a swelling or dimpling. This can usually be avoided by regularly changing the injection site.

The most serious risk of treatment with medicaments for diabetics is an excessive reduction in the blood glucose level. This is usually caused by insufficient food intake, particularly if a person taking insulin misses a meal or snack, or takes unaccustomed exercise. Unless compensating action is taken, the diabetic may lose consciousness; in rare circumstances prolonged hypoglycemia may result in seizures or brain damage. Diabetics should always carry glucose tablets or candy to take if warning symptoms of hypoglycemia occur. People who take insulin may also be advised to carry glucagon, a medicament which rapidly increases the blood glucose level by blocking the effects of insulin, together with instructions for its use in the event of loss of consciousness.

Because exercise increases the body's glucose requirement, extra glucose may be needed before undertaking unaccustomed physical activity. Serious illness often increases the need for insulin, and dosage may need to be increased until after recovery. A woman taking sulfonylurea medicaments who wishes to become pregnant should discuss her medicament treatment with a physician before conceiving because these medicaments can cross the placenta and affect the developing baby; a temporary change to insulin treatment until after the baby is born is advised.

There are many types of insulin preparations, each available in different strengths. It is important that you receive exactly the same one each time you renew your prescription, since the dosage is tailored for your needs. You will be given an identification card stating type of medicament and dosage.

Medicaments for thyroid disorders

The thyroid gland, located in the neck, produces hormones that regulate metabolism. During childhood, thyroid hormones are essential for normal mental and physical development. The thyroid also produces calcitonin, a hormone involved with normal calcium balance.

The thyroid gland can become overactive, producing excess amounts of hormones, causing a condition known as hyperthyroidism or thyrotoxicosis. The gland can also become underactive, producing insufficient hormones, a condition called hypothyroidism.

Medicaments for thyrotoxicosis
Antithyroid medicaments reduce production of thyroid hormones to near normal levels. These medicaments may take about four to six weeks to produce any effect, because the thyroid gland contains a store of hormones that is only gradually depleted. Therefore, a beta blocker may be prescribed to control symptoms at the beginning of treatment.
A course of antithyroid medicament treatment is usually started with a high dose to give a rapid improvement in symptoms; the dosage is gradually reduced, depending on the individual response. Some people recover completely after one course of treatment, but symptoms may return, especially in children, making further treatment necessary. Antithyroid medicaments may not improve exophthalmos, although they may prevent it from worsening. To relieve this condition a corticosteroid may be given. Surgery may be necessary.
The initial high dose of an antithyroid medicament may occasionally produce nausea, vomiting, headache, or skin rashes. More seriously, these medicaments may reduce the white blood cell count, thus increasing susceptibility to infection, and causing recurrent fevers and sore throats. Such symptoms need prompt medical advice. Radioactive iodine may also be used for the treatment of hyperthyroidism; occasionally, surgery is advised.

Medicaments for hypothyroidism
Hypothyroidism is usually permanent, necessitating lifelong treatment with synthetic thyroid hormone preparations. These are usually given by mouth, but may be given by injection or by using a nasogastric tube if an individual's level of thyroid hormone falls so low that consciousness is lost.
Babies are routinely checked after birth for thyroid deficiency because low levels may cause cretinism -permanent mental and physical retardation. If the level is low, a thyroid medicament is injected immediately and administered at regular intervals thereafter. Prompt treatment should establish normal development.
Thyroid medicaments do not usually produce adverse effects, since they are simply supplying a substance that the body would normally produce. However, if the dose is too high, symptoms of thyrotoxicosis may arise. Regular blood tests are usually performed to check that the correct dose is being given. It is common practice to start with a low dose of the medicament and to increase it gradually. A sudden rise in hormone levels can put a strain on the heart. For this reason, thyroid medicaments are prescribed with caution to the elderly and those with heart disease or high blood pressure. A beta blocker may also be given to reduce adverse effects on the heart.

Medicaments for pituitary disorders

The pituitary gland, which lies at the base of the brain, produces a number of hormones that regulate physical growth, metabolism, sexual development, and reproductive function. Many of these hormones act indirectly by stimulating other glands, such as the thyroid, adrenal glands, ovaries, and testicles, to release their own hormones.

An excess or a lack of a pituitary hormone may produce serious effects, the nature of which depends on the hormone involved. Abnormal levels of a particular hormone may be caused by a pituitary tumor sometimes treated surgically. In other cases, medicaments may be used to correct the hormonal imbalance.

The more common pituitary disorders that can be treated with medicaments are those involving growth hormone, antidiuretic hormone, prolactin, adrenal hormones, and the gonadotropins. Lack of corticotropin, leading to inadequate production of adrenal hormones, is usually treated with corticosteroid medicaments.

Medicaments for growth hormone disorders
Growth hormone (somatropin) is the principal hormone required for normal growth in childhood and adolescence. Lack of growth hormone impairs normal physical growth, a condition known as pituitary dwarfism. Physicians administer growth hormone only after tests have shown that a lack of this hormone is the cause of the disorder. If treatment begins early, regular injections of hormone until the end of adolescence usually allow normal growth and development to take place.
Less often, the pituitary produces an excess of growth hormone. In children this can result in pituitary gigantism; in adults, it can produce a deformity known as acromegaly. Acromegaly is usually the result of a pituitary tumor and is characterized by thickening of the skull, face, hands, and feet, and the enlargement of some internal organs.
Although these conditions cannot be cured, gigantism may be halted and some of the deformities of acromegaly reversed by reducing the output of growth hormone. This is usually achieved by destroying part of the pituitary gland, either by surgery or radiation treatment. The medicament bromocriptine, which reduces growth hormone levels, is also used.

Medicaments for diabetes insipidus
Antidiuretic hormone (also known as ADH or vasopressin) acts on the kidneys, controlling the amount of water retained in the body and returned to the blood. A lack of ADH is usually caused by damage to the pituitary, and this in turn causes diabetes insipidus. In this rare condition, the kidneys cannot retain water, and large quantities pass into the urine. The chief symptoms of diabetes insipidus are constant thirst and the production of large volumes of urine.
Diabetes insipidus is treated with vasopressin or desmopressin. Vasopressin has to be given by injection. Desmopressin, an artificial form of vasopressin, is inhaled from a nasal spray. Mild cases of this disease may be treated either with clofibrate, which increases the amount of ADH released by the pituitary, or chlorpropamide, which also increases ADH release. In addition the medicament makes the kidneys more sensitive to the hormone. Alternatively, a thiazide-like diuretic (such as chlorthalidone) may be prescribed for mild cases. The usual effect of such medicaments is to increase urine production, but in diabetes insipidus they have the opposite effect, reducing water loss from the body.

Medicaments used to reduce prolactin levels
Prolactin, or lactogenic hormone, is produced in both men and women. In women, prolactin controls the secretion of breast milk following childbirth; its function in men is not understood, although it appears to be necessary for normal sperm production. The disorders associated with prolactin are all concerned with overproduction. High levels of prolactin in women can cause lactation unassociated with pregnancy and birth (galactorrhea), lack of menstruation (amenorrhea), and infertility. If excessive amounts are produced in men, the result may be galactorrhea and/or infertility. Some medicaments, notably phenothiazine antipsychotics, estrogen, and methyldopa, can all raise the level of prolactin in the blood. More often, however, increased prolactin results from a pituitary tumor that is sometimes treated surgically. Bromocriptine inhibits the production of prolactin and is also used in the treatment of prolactin tumors.

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