Signs and Symptoms of Hypothyroidism
- Poor ability to tolerate cold
- Feeling tired
- Constipation
- Weight gain
- Swelling of the front part of the neck due to goitre

Diagnosis and Treatment of Hypothyroidism
- Blood tests measuring thyroid-stimulating hormone (TSH) and thyroxine levels confirm the diagnosis
- Salt iodization has helped prevent hypothyroidism in many populations
- Thyroid hormone replacement with levothyroxine is the main treatment
- Dose adjustment is based on symptoms and normalization of thyroxine and TSH levels
- Thyroid medication is safe during pregnancy

Prevalence and Demographics of Hypothyroidism
- Worldwide, iodine deficiency in the diet is the most common cause of hypothyroidism
- Hashimoto's thyroiditis is the most common cause in countries with sufficient dietary iodine
- Other causes include previous treatment with radioactive iodine, hypothalamus or anterior pituitary gland injury, certain medications, lack of a functioning thyroid at birth, or previous thyroid surgery
- About one billion people worldwide are estimated to be iodine-deficient
- In the United States, hypothyroidism occurs in 0.3-0.4% of people

Effects of Hypothyroidism on Pregnancy
- Untreated hypothyroidism during pregnancy can lead to delays in growth and intellectual development in the baby
- Even mild or subclinical hypothyroidism can increase the risk of infertility and miscarriage
- Hypothyroidism in early pregnancy may increase the risk of pre-eclampsia and lower intelligence in offspring
- Subclinical hypothyroidism during pregnancy is associated with gestational diabetes, low birth-weight, placental abruption, and preterm birth
- Hypothyroidism affects 0.3-0.5% of pregnancies in women

Related Disorders and Complications of Hypothyroidism
- Thyroid hormone abnormalities are common in major psychiatric disorders, such as bipolar disorder, mood disorders, and schizophrenia-spectrum disorders
- Screening for thyroid dysfunction is recommended among individuals with psychiatric disorders
- Myxedema coma is a rare but life-threatening state of extreme hypothyroidism
- Myxedema coma can occur in those with established hypothyroidism during acute illness
- Myxedema coma is characterised by low body temperature, confusion, slow heart rate, reduced breathing effort, and physical signs of hypothyroidism

Hypothyroidism (Wikipedia)

Not to be confused with Hyperthyroidism.

Hypothyroidism (also called underactive thyroid, low thyroid or hypothyreosis) is a disorder of the endocrine system in which the thyroid gland does not produce enough thyroid hormones. It can cause a number of symptoms, such as poor ability to tolerate cold, a feeling of tiredness, constipation, slow heart rate, depression, and weight gain. Occasionally there may be swelling of the front part of the neck due to goitre. Untreated cases of hypothyroidism during pregnancy can lead to delays in growth and intellectual development in the baby or congenital iodine deficiency syndrome.

Hypothyroidism
Other names	Underactive thyroid, low thyroid, hypothyreosis
Molecular structure of thyroxine, which is deficient in hypothyroidism
Pronunciation	/ˌhaɪpəˈθaɪrɔɪdɪzəm, -poʊ-/
Specialty	Endocrinology
Symptoms	Poor ability to tolerate cold, feeling tired, constipation, weight gain, depression, anxiety, irritability
Complications	During pregnancy can result in cretinism in the baby
Usual onset	< 60 years old
Causes	Iodine deficiency, Hashimoto's thyroiditis
Diagnostic method	Blood tests (thyroid-stimulating hormone, thyroxine)
Differential diagnosis	Depression, dementia, heart failure, chronic fatigue syndrome
Prevention	Salt iodization
Treatment	Levothyroxine
Frequency	0.3–0.4% (USA)

Worldwide, too little iodine in the diet is the most common cause of hypothyroidism. Hashimoto's thyroiditis is the most common cause of hypothyroidism in countries with sufficient dietary iodine. Less common causes include previous treatment with radioactive iodine, injury to the hypothalamus or the anterior pituitary gland, certain medications, a lack of a functioning thyroid at birth, or previous thyroid surgery. The diagnosis of hypothyroidism, when suspected, can be confirmed with blood tests measuring thyroid-stimulating hormone (TSH) and thyroxine levels.

Salt iodization has prevented hypothyroidism in many populations. Thyroid hormone replacement with levothyroxine treats hypothyroidism. Medical professionals adjust the dose according to symptoms and normalization of the thyroxine and TSH levels. Thyroid medication is safe in pregnancy. Although an adequate amount of dietary iodine is important, too much may worsen specific forms of hypothyroidism.

Worldwide about one billion people are estimated to be iodine-deficient; however, it is unknown how often this results in hypothyroidism. In the United States, hypothyroidism occurs in 0.3–0.4% of people. Subclinical hypothyroidism, a milder form of hypothyroidism characterised by normal thyroxine levels and an elevated TSH level, is thought to occur in 4.3–8.5% of people in the United States. Hypothyroidism is more common in women than in men. People over the age of 60 are more commonly affected. Dogs are also known to develop hypothyroidism, as are cats and horses, albeit more rarely. The word hypothyroidism is from Greek hypo- 'reduced', thyreos 'shield', and eidos 'form'.