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Difference between Hypothyroidism and Hyperthyroidism

Both hypothyroidism and Hyperthyroidism affect the thyroid gland but have opposite effects on the body. The thyroid gland is a tiny, butterfly-shaped gland located at the base of the front of the neck. It acts as the control center for the body. It secretes various hormones which help maintain the brain, heart, lungs and various other organs of the body. Sometimes due to some reasons, the gland starts overproducing or underproducing the thyroid hormones which lead to hyperthyroidism and hypothyroidism respectively. Let us see how one differs from another!


Hypothyroidism refers to the underactive thyroid gland, meaning the thyroid gland is not able to produce enough thyroid hormones. It slows down body's metabolism which means you will burn fewer calories which may lead to weight gain. The most common cause of hypothyroidism is Hashimoto's thyroiditis. It is a condition in which body's immune system starts attacking and damaging the thyroid gland and thus affects its ability to produce thyroid hormones. In hyperthyroidism, the level of T3 and T4 thyroid hormones decreases but the level of TSH increases. It can occur at any age but the risk increases as you get older. It is also caused by genetic predisposition and women are three times more likely to develop hypothyroidism than men.

Generally, the Levothyroxine sodium tablets are used as a replacement hormone to regulate thyroid levels. It contains synthetic thyroid hormone similar to thyroxine produced by the thyroid gland.

Common causes of hypothyroidism:

  • Muscle cramps
  • Goitero
  • Brittle nails
  • Irregular periods
  • Slow heart rate
  • Constipation
  • Carpal tunnel syndrome


Hyperthyroidism refers to the overactive thyroid gland, meaning the thyroid gland produces too much thyroid hormone. In hyperthyroidism, there is an increase in the levels of T3 and T4 hormones and but the level of TSH is decreased.

Generally, Methimazole or Propylthiouracil (PTU) is used to treat hyperthyroidism. It signals the thyroid to slow down the production of T3 and T4 hormones. It comes in a tablet form. If medicine does not work, surgery may be performed to remove some part of the thyroid or radioactive iodine treatment can be used.

Common causes:

  • A thyroid nodule that produces too much T4 hormone and tends to increase the thyroid size.
  • An autoimmune condition known as Graves' disease stimulates the production of T4 and T3 thyroid hormones.

Symptoms of hyperthyroidism:

  • Unexplained weight loss
  • Feeling wired or anxious
  • Shakiness
  • Itchy skin
  • High heartbeat
  • Hair loss
  • Frequent bowel movements
  • Intolerance to heat
  • High metabolic rate

Based on the above information, some of the key differences between hypothyroidism and hyperthyroidism are as follows:

Hypothyroidism Hyperthyroidism
The thyroid gland becomes underactive and cannot produce enough thyroid hormones. The thyroid gland becomes overactive and overproduces thyroid hormones.
It increases the level of thyroid hormones. It decreases the level of thyroid hormones.
It does not lead to thyrotoxicosis and grave's disease. It can lead to thyrotoxicosis and grave's disease.
It slows down the metabolism. It increases the metabolism.
It is treated by supplements containing synthetic thyroid hormones like levothyroxine or thyroxine. It is treated by anti-thyroid drugs, radioactive iodine therapy etc.
It shows decreased levels of T3 and T4 hormones. It increases the levels of T3 and T4 hormones.
It increases the level of TSH. It decreases the level of TSH.
It is mostly an inherited disease. Common causes are thyroiditis and grave's disease.
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