Hypothyroidism

What is it?

According to the NIDDK: “hypothyroidism is when the thyroid gland does not make enough hormones to meet your body's needs”. The gland controls how the body uses energy and affects almost every organ. It affects about 5 in 100 Americans aged 12 and over, and most cases are mild with few noticeable symptoms.

MedlinePlus states that the gland regulates energy use and affects breathing, heart rate, weight, digestion and mood.

Causes

According to the NIDDK: the most common causes are Hashimoto disease, then thyroiditis (three types: subacute, postpartum and silent), congenital hypothyroidism, surgical removal of the gland, radiation treatment, certain medicines (for the heart, bipolar disorder and cancer), and rarely iodine deficiency or pituitary and hypothalamic diseases.

Hashimoto disease, according to the NIDDK, is an autoimmune disorder in which the immune system makes antibodies that attack the gland so it cannot produce enough hormones, and it is the most common cause of hypothyroidism. Its cause is not fully known; genetic factors, viral infection (such as hepatitis C), certain medicines and iodine-containing treatments, and exposure to toxins including nuclear radiation are listed.

Risk factors

According to the NIDDK: women and people over 60, previous thyroid problems or surgery or radioactive iodine treatment, radiation exposure to the thyroid, neck or chest, a family history of thyroid disease, giving birth within the past six months, Turner syndrome, and autoimmune diseases (coeliac disease, Sjögren syndrome, pernicious anaemia, type 1 and 2 diabetes, rheumatoid arthritis and lupus).

The NIDDK states that Hashimoto disease is 4 to 10 times more common in women, and usually appears at ages 30 to 50.

Symptoms

According to the NIDDK: exhaustion, weight gain, cold intolerance, joint and muscle pain, dry skin, hair loss, menstrual disturbance, fertility problems, slow pulse and depression. Symptoms develop slowly over months or years. MedlinePlus adds a puffy face, constipation and an enlarged gland (goitre).

The NHS also lists difficulty concentrating, low mood and a hoarse voice. The symptoms resemble those of other conditions.

How is it diagnosed?

According to the NIDDK, diagnosis is not based on symptoms alone: medical history, clinical examination and thyroid blood tests, with imaging tests to confirm the diagnosis and find the cause.

Blood tests (NIDDK): TSH is a pituitary hormone that tells the gland how much T4 and T3 to make; a rise usually indicates deficiency. A low T4 may indicate deficiency, and “free T4” is preferred by many because it reflects function more accurately. Antibody tests diagnose autoimmune disorders such as Hashimoto. MedlinePlus also lists the T3 test and imaging (thyroid scan, ultrasound and radioactive iodine uptake test). In Hashimoto, ultrasound may confirm the diagnosis if antibodies are absent.

• TSH testLab test

Treatment

The treatment categories usually used are listed here; this is not a prescription. The doctor chooses the plan according to each person's condition; do not change any medicine or dose without a specialist.

According to the NIDDK: it is treated with levothyroxine, a hormone “identical to the one a healthy thyroid makes”, available as tablets, liquid or soft gel capsules. Blood is tested after 6 to 8 weeks, then after 6 months, then yearly to adjust the dose. The NHS states that it is often lifelong and that follow-up prevents side effects such as nausea, diarrhoea, headache and sleep disturbance. The doctor determines the medicine and dose according to the tests, and do not change your medicine without a specialist.

Pregnancy (NIDDK): untreated hypothyroidism affects the mother and the fetus, thyroid medicines are safe in pregnancy, and many women need a higher dose as directed by the doctor.

Diet (NIDDK): people with Hashimoto or an autoimmune thyroid disorder may be sensitive to iodine, so seaweed and algae are avoided; pregnant women need more iodine. Substances that may hinder medicine absorption include grapefruit juice, soy, and multivitamins containing iron and calcium (Hashimoto page).

Complications

According to the NIDDK: high cholesterol, and rarely myxoedema coma in severe untreated cases, which requires immediate medical care. The Hashimoto page adds heart disease, heart failure and high blood pressure. The NHS lists heart and bone problems and osteoporosis, and pregnancy complications (pre-eclampsia, birth defects and miscarriage) when untreated or poorly controlled; MedlinePlus lists miscarriage and impaired fetal development.

Living with it

In Hashimoto the NIDDK advises adherence to the medicine and regular follow-up with blood tests. The NHS offers support through British patient organisations that are not adopted here.

Common questions