Partial or total loss of thyroid gland function due to inadequate synthesis or resistance to the action of thyroid hormones. Since these molecules play a vital role in almost all tissues, their decrease or absence will manifest itself in a multitude of body systems. It is one of the most common diseases worldwide, affecting up to 5% of the population.

There may be several causes related to hypothyroidism:

  • Autoimmune disorders: the most common cause of hypothyroidism is Hashimoto's thyroiditis due to the production of antibodies to the thyroid gland. However, the exact triggers of this disease are unknown, although a combination of genetic and environmental factors has been suggested.
  • Response to treatment for hyperthyroidism with radioactive iodine or antithyroid medications used to normalize thyroid function that triggers permanent hypothyroidism.
  • Thyroid surgery involving removal of all or part of the thyroid gland.
  • Radiation therapy treatment for head and neck cancer.
  • Medications used in the treatment of other diseases (amiodarone, lithium, interferon-alpha, interleukin-2).
  • Thyroiditis or inflammation of the thyroid gland due to infections, congenital disease of defective or absent thyroid gland, or disorders of the pituitary gland involving absence of stimuli on the thyroid gland, infiltrative thyroid disorders.
  • Pregnancy can trigger the production of antibodies against the thyroid gland. If left untreated, it can increase the risk of miscarriage, premature delivery and preeclampsia or fetal development.
  • Iodine deficiency since it is essential for the production of thyroid hormones. Iodine deficiency can lead to hypothyroidism, while excess iodine can worsen existing hypothyroidism.

In addition, a number of factors have been described that may increase the risk of hypothyroidism:

  • Age: the risk increases with age, especially after the age of 60.
  • Gender: women have a higher risk of hypothyroidism than men.
  • Having other autoimmune diseases such as type 1 diabetes, celiac disease, rheumatoid arthritis.

Heritability studies have suggested that up to 67% of circulating thyroid hormone and TSH concentrations are genetically determined, however, the genetic causes associated with a loss of function including those of autoimmune origin are unknown. For this reason, the UK Biobank project has evaluated the genetic associations related to the development of hypothyroidism in almost 15,000 cases and more than 400,000 controls, and as a result up to 45 risk loci related to this condition have been identified.


Signs and symptoms of hypothyroidism vary depending on the severity of the hormone deficiency and may vary from person to person. In early stages, the symptoms of hypothyroidism are barely noticeable, and as the disease slowly progresses they become more evident Some common symptoms include:

  • Fatigue and tiredness.
  • Weight gain.
  • Cold tolerance problems.
  • Joint and muscle pain, cramps.
  • Dry, flaky skin, brittle and weakened hair and nails.
  • Loss of libido.
  • Irregular or heavy menstrual periods, fertility problems.
  • Slow heart rate.
  • Depression.
  • Slow movements and thinking.
  • constipation
  • elevated cholesterol levels
  • swelling of the face, hands, and feet.

In addition, children may experience slower growth and development, adolescents may begin puberty earlier than normal, and older people may develop memory problems in addition to depression.


Hypothyroidism cannot be prevented, but it is easily manageable if detected early and properly treated. The best way to prevent a severe form of the disease or for symptoms to limit your quality of life is to be aware of possible symptoms and if you experience any, see your doctor.

Number of observed variants

13.5 million variants

Number of risk loci analyzed in the study

44 loci

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