Thyroid, its functions, its disorders and treatments

Thyroid is a large butterfly shaped endocrine gland situated in the neck close to the trachea. The gland consists of two elongated oval lobes joined by a narrow band called isthmus. It is a highly vascular organ and contains many spherical or oval sac like follicles. Cells lining the thyroid follicles secretes thyroid hormones, thyroxine (T4) and triiodothyronine (T3). Both are iodinated forms of an amino acid called TYROSINE and remain stored in the jelly like semi fluid material (colloid) in the lumen of follicles. T3 is more active and several times more potent than T4. T4 is mainly secreted from thyroid and converted to T3 in peripheral tissues e.g., Liver. Thyroid is the only endocrine gland which stores its products in large quantity. The hormones are released from the colloid to the blood when necessary. C-cells or Parafollicular cells are present between thyroid follicles which release calcitonin or parafollicular hormone. It is involved in calcium homeostasis. It is hypocalcemic and hypophosphatemic. Both parathormone and calcitonin help in the maintenance of calcium ions in blood plasma.

The Functions of thyroid gland are precisely discussed below:

ü  Thyroid hormones greatly increase the metabolic rate of the body and consequently, enhance heat production (Calorigenic effect) and maintains BMR (Basal metabolic rate).

ü  Thyroid hormone also promote growth of the body tissues-both physical growth and development of mental faculties are stimulated.

ü  They stimulate tissue differentiation and for this they promote metamorphosis of tadpoles into adult frogs.

ü  They enhance some actions of neurotransmitter: adrenaline and nor-adrenaline.

DISORDERS DUE TO THYROID HORMONE IMBALANCES:

HYPOTHYROIDISM

1.      CRETINISM: It is the failure of thyroid secretion from infancy or childhood which slows body growth and mental development and reduces metabolic rate markedly. The child remain physically stunted and mentally retarded. The body temperature, heart rate and blood pressure of the patient remain lower than normal. The patient is pot-bellied and pigeon chested and has a protruding tongue. Other features include neonatal jaundice, lethargy respiratory problems and constipation. This disease is called CRETINISM. Normal growth and development may be restored in certain cases by early administration of thyroid hormones.

2.      MYXEDEMA (Gull’s Disease): Deficiency of thyroid hormones produces MYXEDEMA in adults. The patient has a puffy appearance and lacks alertness, intelligence and initiative. The patient also suffers from low metabolic rate, slow heart rate, low body temperature and reproductive failure. Administration of thyroid hormones cures the symptoms. It occurs more commonly in females.

3.      SIMPLE GOITRE: It is the enlargement of thyroid gland due to the deficiency of iodine. It is commonly occurs in mountainous regions because of the dietary deficiency of iodine. It is accompanied by CRETINISM or MYXEDEMA.

HYPERTHYROIDISM

1.      EXOPHTHALMIC GOITRE or GRAVE’s DISEASE: In this disease, a thyroid enlargement (Goitre) is accompanied by a bulging of eyeballs (Exophthalmos). The enlarged thyroid becomes overactive and secretes excessive amount of thyroid hormones. So, the goitre is associated with the symptoms of thyroid overactivity such as high metabolic rate, rapid heart rate, rise in body temperature, emaciation, nervousness, irritability, tremor and restlessness. It also occurs more often in females. It is an autoimmune disorder in which the person produces antibodies that mimic the action of TSH (Thyroid Stimulating Hormone) but are not regulated by normal negative feedback controls.

Proper diet and consumption of nutrients rich foods can be the preventive method to safeguard children and teenagers from thyroid problems as ‘PREVENTION IS BETTER THAN CURE’.

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