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Thyroid is an endocrine gland, mesodermal in origin, present behind the neck. It is brownish in colour and consists of two lobes, both joined by a thyroid isthmus. Each lobe consists of numerous follicles. It makes and stores hormones that regulates the heart rate, blood pressure, body temperature and the rate at which food is converted into energy. Thyroid hormones are essential for the function of every cell in the body.

HORMONES produced by the thyroid gland –

· T₄– known as tetra iodothyroxine

· T₃– known as triiodothyroxine

Together the T₃and T₄are known as thyroxine hormone. These are iodinated derivatives of the amino acid, tyrosine. These are secreted by the follicles of the gland.

FUNCTIONS –

· It controls the basal metabolic rate (BMR) of the body.

· It also controls the physical, sexual and mental growth of the body

· Contributes in the kidney mechanism and formation of urine

· Checks over the maintenance of water – electrolyte balance of the body

· Helps in maintaining a normal body temperature

DISORDERS –

An increase in the levels of thyroxine causes hyperthyroidism whereas a decrease in the levels causes hypothyroidism. Here are a few examples –

1. Cretinism –

· It is a condition occurring in children when the levels of thyroxine reduces before puberty, i.e., it is a condition due to hypothyroidism in kids.

· The child remains dwarf

· Reduced mental development

· Reduced metabolism

· The child shows a Pot belly, dry skin, thick protruding tongue

2. Myxedema (also known as Gull’s Disease) –

· It is a condition encountered by adults due to hypothyroidism

· Oedema / edema, i.e., accumulation of interstitial fluid.

· It causes swelling in the face and the person looks fluffy

· It is marked by low metabolic rate, lethargy, loss of hair, slow heart beat and low body temperature

3. Goitre –

It is caused due to deficiency of iodine. The thyroid gland appears enlarged. It can also be accompanied by cretinism or myxedema.

4. Exophthalmic goitre (also known as Grave’s disease)

· It is a condition caused by hyperthyroidism

· The eye balls appears bulging and it is marked by weight loss, increased BMR and high body temperatures.

This was a summary of thyroid – the gland, its hormones and the deficiency diseases. I hope this helps.