Melatonin and Thyroid Disorders

Hypothyroidism and hyperthyroidism are the most frequent disorders of the thyroid gland. In hyperthyroidism, the thyroid gland secretes excessive thyroid hormone while in hypothyroidism; the amount of thyroid hormone is inadequate. Both disorders have been associated with cell damage. Melatonin which is a sleep-regulating hormone protects the cell against damage. But it can also down-regulate the activity of the thyroid gland. Thus, melatonin can make hypothyroidism become worse.

Oxidative Stress

Oxygen is needed in converting the components of food into energy so that the body can use it. Even if this metabolic process is important to stay alive, this will also produce toxic and unstable byproducts termed as free radicals. When electrons are eliminated from an atom or molecule, free radicals are produced. They also absorb electrons from other cell molecules. This will result to a condition called oxidative stress because of cell damage and abnormalities in the growth of cells. Antioxidants like vitamins C and E, beta carotene and selenium are helpful in preventing cell damage by providing an electron to the free radicals.


An overactive thyroid commonly occurs as a result of an autoimmune disorder. In this condition, the immune system attacks the thyroid gland. In some rare instances, hyperthyroidism can be a result of a non-cancerous tumor in the thyroid gland or from a thyroid gland infection. This happens due to an increased secretion of T3 and T4 thyroid hormones. If there is too much thyroid hormones in the bloodstream, the metabolic rate will increase. Oxidative stress is caused by hyperthyroidism since higher amounts of oxygen for the production of the necessary energy is important for higher metabolism.


An underactive thyroid is usually an autoimmune condition or a result of the treatment for hyperthyroidism in which the thyroid gland is removed or it is treated with radioactive iodine. If the thyroid gland is underactive, secretion of thyroid hormones T3 and T4 into the bloodstream will be in smaller amounts. Hence, metabolism is decreased. It is still unclear whether or not hypothyroidism leads to oxidative stress. It was found out in the study published by Clinical Chemistry and Laboratory Medicine in their November 2010 issue that hypothyroidism has correlation to increased levels of low-density lipoprotein or bad cholesterol resulting to oxidative stress. Therefore, hypothyroidism can be an indirect cause of oxidative stress.


This is taken from the mood-enhancing neurotransmitter serotonin located in the pineal gland. This controls the sleep rhythm within 24 hours and is frequently used for the prevention of jet lag, to modify the sleep rhythm in individuals who work at nightshifts and also to cure sleep disorders. As a potential antioxidant, this is used in preventing oxidative stress. Based on the review published in Neuro Endocrinology Letters in their April 2002 issue, melatonin is capable of down-regulating the thyroid gland activity. Hence, melatonin is useful as a supplement for those suffering from hyperthyroidism. But melatonin supplement should not be used if a person has hypothyroidism since this can only make the condition worse.

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