Thyroid Hormone - Get to know your hormones

Thyroid Hormone - Get to know your hormones

Thyroid hormone is an essential hormone in the body. It is produced by the thyroid gland located at the front of your neck and is shaped like two wings (lobes) of a butterfly connected by a bridge called theisthmus. Depending on the size of your thyroid gland it can sometimes be felt. However, if you notice it changing in size or feel a lump, you should ask your doctor to review it.

What does thyroid hormone do?

Thyroid hormone’s main function is to regulate your body’s metabolism, temperature regulation and growth. Metabolism is the process of converting carbohydrates, fats and proteins into energy that the body then uses for activities such as heat generation, muscle turnover, growth and development. Below is a list of thyroid hormone’s effects: 

  1. Heart – increases heart rate and how much blood is pumped around the body,
  2. Muscles – increases the speed of muscle contraction, relaxation and replacement*,
  3. Liver – increases breakdown of energy stores so more carbohydrates (glucose) are readily available,
  4. Bones – increases bone turnover (the cycle of bone building and breakdown)*,
  5. Gut – increases gut movement and carbohydrate absorption,
  6. Fat – increases breakdown of fats,
  7. Mood – effects memory functions, and increases anxiety and irritability,
  8. Other hormones – works in conjunction with other hormones such as insulin and cortisol to cause the effects above

 How is thyroid hormone controlled?

Production of thyroid hormone is controlled by another hormone called thyroid-stimulating hormone (TSH), released from the pituitary gland in the brain. This is finely balanced, depending on the metabolic demands of your body and levels of thyroid hormone in your blood. TSH rises and falls to control the levels of thyroid hormone in the blood depending on whether the body needs to produce more energy. This regulating system is called a ‘feedback loop’.

Thyroid hormone during menopause

Like oestrogen, thyroid hormone controls many functions in the body and disorders of thyroid hormone can cause symptoms similar to those during menopause. Symptoms such as irregular or heavy periods, palpitations, low mood, anxiety, irritability, memory loss, sleep disorders ,weight gain and muscle pain can be caused by either. Women are more likely to develop thyroid conditions, and this most frequently occurs during times of hormonal flux, such as menopause, puberty, and pregnancy. Hypothyroidism (low thyroid hormone) is commonly discovered around 50-60 years old, for this reason your GP may test your thyroid hormones around menopause.

Thyroid hormone (thyroxine), supplements and HRT

Oestrogen and thyroid hormone interact with each other making it important to tell your doctor if you are taking thyroxine before starting HRT. The oestrogen in oral HRT causes our livers to increase thyroxine-binding globulin, a substance that transports and deactivates thyroid hormone, thus decreasing the levels of thyroxine for our body to use. This relationship isn’t of any concern if you have normal thyroid function.

If you are taking calcium supplements, it is vital that you take them separately to your levothyroxine. Studies have shown that calcium interferes and reduces absorption of the medication from your gut. To avoid this, leave 4 hours between taking your medication and calcium.

To read more in this series, visit:

  1. An introduction to hormones
  2. Oestrogen and Progesterone
  3. Testosterone
  4. Cortisol


*thyroid hormone levels in the body are finely balanced, in hyperthyroidism when there is too much thyroid hormone, this can lead to excess muscle and bone loss. You can read more about hyperthyroidism and hypothyroidism here:




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