The Thyroid, the forgotten gland? – South Coast Herald

The thyroid gland is a butterfly-shaped gland located in the front of the neck covering the voice box (larynx) and the windpipe (trachea). This gland is important in all metabolic functions in the body and its importance is often under appreciated. The thyroid gland produces several hormones: triiodothyronine, thyroxine, and calcitonin. Iodine and tyrosine are needed to produce these hormones. The secretion of these hormones is influenced by the thyroid itself and is regulated by the Thyroid Stimulation Hormone (TSH) produced in the pituitary gland in the brain, which is in turn regulated by Thyrotropin Releasing Hormone (TRH) produced by the hypothalamus. The thyroid hormones provide negative feedback to TSH and TRH: when the thyroid hormones are high, the TSH production is suppressed and vice versa. TRH is also secreted at an increased rate in situations such as cold exposure to stimulate thermogenesis (the generation of heat).

Calcitonin helps to regulate blood calcium levels, if the blood calcium level is high, calcitonin decreases the release of calcium from bone by lowering the activity of bone cells (osteoclasts) that break down bone.

The main function or effect of these thyroid hormones on the body, can be summarised as follows:

DevelopmentThyroid hormones are needed for normal development, and the growth rate in young people. A lack of thyroid hormones in a pregnant female, has detrimental effects on the brain maturation of the fetus and the first few years after birth. A baby born without thyroid producing hormones, will develop severe pathology and the condition is called cretinism.

MetabolicThyroid hormones increase the basal metabolic rate. Appetite, gut motility, and the absorption of substances are influenced by it. It decreases cholesterol by increasing the secretion of cholesterol in bile. Therefore, if the thyroid is under-active, a patients cholesterol might increase as a result.

CardiovascularThe rate of the heartbeat and strength of the hearts contraction are influenced by thyroid hormones as well. The consumption and intake of oxygen and rate of breathing are therefore influenced.

EndocrineSleep and thought patterns, as well as sexual function (libido) and a normal menstrual cycle is dependent on the normal functioning of the thyroid hormones.

Functional disorders of the thyroid include hyperthyroidism as well as hypothyroidism:

Hyperthyroidism is the excessive production of thyroid hormones resulting in an overactive gland. It can cause weight loss, an increased appetite, insomnia, intolerance to heat, palpitations, anxiety, and heart rhythm abnormalities (atrial fibrillation) as well as hair loss. Causes of hyperthyroidism are Graves disease, a toxic multinodular goiter (enlarged thyroid gland with a nodule), thyroid adenoma (growth), inflammation or adenoma in the pituitary gland, the latter causing excess secretion of TSH.

Graves disease is an auto-immune disease resulting in an overproduction of thyroid hormones (with all its associated symptoms) and possible eye and skin problems. Antibodies are produced against the TSH receptor.

Long term management of hyperthyroidism may include medication suppressing thyroid hormones, alternatively radio-active iodine can be given to destroy the thyroid or removal of the thyroid (thyroidectomy) can be considered. Radio-active iodine and a thyroidectomy will result in a permanent lack of thyroid hormones and chronic thyroid medication will be needed as replacement.

Hypothyroidism is the term referring to an underactive thyroid gland. Iodine deficiency is a common cause of hypothyroidism. Hashimotos thyroiditis (auto-immune disease) is also a reason for the underproduction of thyroid hormones. Common symptoms of hypothyroidism are weight gain, tiredness, hair loss, cold intolerance, constipation. In some cases, it can result in myxedema (swelling of the skin and tissues) and in severe cases, a myxedema coma.

Hypothyroidism can be treated with the replacement of thyroid hormones. The cause of hypothyroidism should be established and corrected if possible (iodine deficiency). In some cases, it is transient, as is sometimes seen in the post-birth period (post-partum thyroiditis) or with sub-acute thyroiditis.

Other pathologies relating to the thyroid gland:

Thyroid nodules are often found in the thyroid gland but only about 5% is cancerous (malignant). An ultrasound will be able to determine if the nodule has a malignant nature or not, followed by a fine needle aspiration of the nodule, to analyse whether the cells are normal or cancerous. Most thyroid cancers are well contained and can be cured upon removal of the gland, in a minority of cases, thyroid cancer can be aggressive and will spread to other organs (anaplastic thyroid cancer) and subsequently has a bad prognosis.

Goiter is a term used to refer to an enlarged thyroid gland. A goiter can be caused by iodine deficiency, Graves disease, Hashimotos thyroiditis, inflammation, or diseases that have an infiltrative nature like sarcoidosis and amyloidosis. The underlying cause of the goiter should be determined and treated; in some cases, it is necessary to remove the thyroid gland surgically.

As part of your annual check-up, remind your general practitioner to palpate your thyroid to check for any nodules or enlargement. Suggest including a thyroid profile blood panel (or at least testing your TSH), when the other routine testing for cholesterol, blood glucose and prostate specific antigen (males) are done. A healthy thyroid is needed for a healthy life!

Dr. Janet Strauss is a Medical Doctor and the Chief Operations Officer at Medwell SA The Home Health Care Specialists. For more information visit http://www.medwell.co.za

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The Thyroid, the forgotten gland? - South Coast Herald