Hypothyroidism (under-active thyroid) is a common disorder that results from thyroid hormone deficiency. The thyroid gland is located in the neck, and produces the hormone thyroxine, that regulates metabolic functions of the body. Because nearly all metabolically active cells require thyroid hormone, deficiency of the hormone has a wide range of effects and an under-active thyroid gland slows the down many functions of the body. World wide, iodine deficiency remains the no.1 cause of hypothyroidism (iodine is an integral component in the chemical make up thyroxine).

Both men and women can have an under-active thyroid. However, it’s more common in women. It is estimated that it affects 15 in every 1,000 women and 1 in 1,000 men. One in 4,500 babies are born with an under-active thyroid (called congenital hypothyroidism).


Symptoms usually begin slowly, and are difficult to detect as they are very general and non specific.


Common symptoms include:

  • being sensitive to cold
  • weight gain
  • constipation
  • depression
  • tiredness
  • slowness in body and mind
  • muscle aches and weakness
  • muscle cramps
  • dry and scaly skin
  • brittle hair and nails
  • heavy or irregular periods

Elderly people with an under-active thyroid may develop memory problems and depression. Children may experience slower growth and development. Teenagers may start puberty earlier than normal.


A blood test called a thyroid function test, looks at levels of thyroid-stimulating hormone (TSH) and thyroxine in the blood.

A high level of TSH and a low level of thyroxine hormone in the blood could mean you have an under-active thyroid.

If your test shows raised TSH but normal thyroxine, it means you may be at risk of developing an under-active thyroid in the future.

An underactive thyroid (hypothyroidism) is usually treated by taking hormone-replacement tablets called levothyroxine.

Levothyroxine replaces the thyroxine hormone which your thyroid does not make enough of.

A blood test measuring your levels of thyroid-stimulating hormone (TSH) will indicate whether you are taking an appropriate dose of levothyroxine. Patients are started on a low dose of levothyroxine, which is then increased gradually depending on response to the hormone and resolution of symptoms.

If testing detects high levels of TSH but you do not have any symptoms or they are very mild, you may not need any treatment. Some people start to feel better soon after beginning treatment, while others can take several months.

An underactive thyroid is a lifelong condition, so you will probably need to take levothyroxine for the rest of your life.

Levothyroxine does not usually have any side effects as the tablets simply replace a missing hormone.

Blood tests are performed once a year, every year, to monitor the dose and response.

Levothyroxine is safe to take during pregnancy, but patients usually require larger doses, and will need more frequent testing to keep a check on hormone levels. 

Dr. Annie

Physician, mom and wife

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