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Thyroid Disorders

THYROID DISORDERS The thyroid gland develops as in embryonic form, from a median outgrowth of the floor of pharynx (windpipe), descends into the front of the neck before birth where it bifurcates and forms the thyroid lobes. Normally the thyroid gland is situated in the front of the neck but sometimes it is partially or wholly behind the sternum (breast bone). The normal adult thyroid gland consists of two lateral lobes joined at the lower poles by an isthmus (thyroid tissue) and weighs between 20 to 30 grams.

Thyroid Disorders

The function of the thyroid gland, which is the largest endocrine gland in the body, is to synthesize, store and secrete the two thyroid hormones:

• Thyroxine (T4) and
• Tri-iodothyronine (T3)

The thyroid gland releases T3 and T4 into the blood stream which transports them through the whole body. These hormones, then, control the metabolism (conversion of calcium and oxygen to energy). The normal thyroid gland produces a mixture of hormones which contain about 80% T4 and only 20% T3.

HYPOTHYROIDISM

In Infants: Congenital deficiency of the thyroid hormones causes cretinism, which is also known as infantile hypothyroidism and is a condition arising from varying degrees of thyroid deficiency in fetal or neonatal stage. It is characterized by retarded development that is particularly marked in the skeletal and central nervous systems.

According to the American Association of Clinical Endocrinology, Infantile hypothyroidism may occur in the endemic or sporadic forms.

The endemic form is found in areas of severe iodine deficiency and, in most cases, the mother of the infant suffers from a goiter.

Sporadic infantile hypothyroidism is rare and is  usually due to a congenital absence of thyroid tissue (a condition called athyreosis) or failure of the embryonic gland to descend in to the neck. The Mayo Clinic, a premier center of thyroid research, says that thyroid deficiency may also arise from a partial or complete absence of one of the several enzymes required for the bio-synthesis of the thyroid hormones. Sporadic infantile hypothyroidism may also occur in an infant born of a hyperthyroid mother who has been treated during pregnancy with too large doses of an antithyroid drug which crosses the placenta and depresses the thyroid activity in  the fetus.s.

In children: In older children, the lack is manifested as juvenile hypothyroidism, also known as  juvenile myxodema, in which dwarfism is a prominent feature. According to the American Thyroid Association, the cause of the hypothyroidism  is not always clear but in some cases, the thyroid gland has not developed properly and ectopic thyroid tissue, which produces sufficient thyroid s to meet the needs of infancy, fails to do so as the child grows.

In Adults: In adults, hypothyroidism is known as myxodema and is much more common in women than in men. The cause of myxodema is often not clear and has in the past been attributed to idiopathic atrophy. It seems that autoimmune processes are at work in most of the cases.

HYPERTHYROIDISM

In healthy people, the thyroid gland produces precise quantities of two hormones, T4 and T3, which have an effect on every aspect of the body's functioning. Research has shown that these hormones control many aspects of our metabolism which, in the final analysis, determines the number of calories a person expends, how warm he feels, and what is his weight. In other words, we can say that the thyroid "runs" our metabolism.

These hormones directly affect most organs, including the heart, which beats faster and harder under the influence of thyroid hormones. All the cells in the body will respond to an increase in the quantity of thyroid hormone by increasing the rate of their working. Hyperthyroidism or thyrotoxicosis is a clinical condition which results from over secretion of thyroidal hormones. It can be due to over-activity of the gland or as a result of localized over-activity due to single hyper-plastic nodule.

The following conditions are attributed to hyperthyroidism:

• Grave's Disease
• Congenital Thyrotoxicosis
• Transient Hyperthyroidism
• Metastatic Thyroid Carcinoma

According to the British Medical Journal and the British Thyroid Foundation, Graves Disease is caused mainly by the over-activity of the thyroid gland. It is the most common cause of hyperthyroidism and together with nodular goiter, it accounts for 99% of the cases. The causes of Grave's Disease are TSH producing tumors or increased production of TSH by a pituitary tumor [1]. Grave's Disease is more common in women than in men and occurs between the ages of puberty and menopause and, very rarely, in children. It is recognized as the consequence of a special type of thyroidal antibody. It may develop as the result of an emotional disturbance.

Congenital Thyrotoxicosis: According to the National Institute of Health, before birth, hyperthyroidism in the fetus may be suspected if the fetal heart rate is unduly rapid and if the mother has been treated in the past for hyperthyroidism.

Transient Hyperthyroidism: This condition may occur in the early stages of Hashimoto's Thyroiditis.

Metastatic thyroid carcinoma:is rare ,some 5 people per million dying from it each year. A lump is grown rapidly in the front of the neck below the Adam,s apple trouble breathing are the main symptoms.

Riedel's thyroiditis and viral thyroiditis are other forms of thyroid disorders.