Hypothyroidism: What It Is, Types, Causes and Signs

The thyroid gland is often associated only with weight, but hypothyroidism is a broader condition. Below is a brief overview: what it is, where it comes from, how it manifests, and how doctors identify it.

What hypothyroidism and underactive thyroid are

Hypothyroidism, also known as hypothyreosis, is a condition in which the thyroid gland produces fewer hormones than the body needs. The gland is small, butterfly-shaped, and lies at the front of the neck. Its hormones control how the body uses energy and affect almost every organ: breathing, heart rate, weight, digestion, mood. When hormones are insufficient, processes slow down. Hence fatigue, feeling cold, weight gain. This is a syndrome, that is, the body's response to a deficiency: remove the deficiency and the manifestations usually resolve.

Types of hypothyroidism: primary, secondary, tissue

Types are distinguished by the site of the problem. Primary, or thyrogenic, means the problem is in the gland itself: there is less functioning tissue, and the synthesis of thyroxine and triiodothyronine is suppressed. Secondary, pituitary, means the pituitary produces little thyrotropin, and the gland does not receive the command. Tertiary, hypothalamic, is related to the hypothalamus and the transport of thyroliberin. Tissue, or transport, means there are enough hormones, but cells respond weakly. There is congenital and acquired hypothyroidism, including postoperative. By severity, primary is divided into latent, when TSH is elevated with normal T4, and overt.

Autoimmune hypothyroidism and other causes

The main culprit is autoimmune thyroiditis, Hashimoto's disease: the immune system attacks its own gland. It is more often a female story, usually starting at age 30–50. Other causes: thyroiditis, congenital hypothyroidism, removal of part or all of the gland, radiation therapy to the neck, treatment for overactive thyroid, some medications, and rarely pituitary disease and iodine imbalances. Risk is higher if:

• you are a woman, especially over 60;
• you have had surgery or radiation to the neck and chest;
• there is thyroid disease in the family;
• you have been pregnant or given birth in the last 6 months;
• you have type 1 diabetes, rheumatoid arthritis, lupus, pernicious anemia, or Sjögren's syndrome.

Overt hypothyroidism and myxedema: how they differ

Overt hypothyroidism is no longer just a number. TSH is elevated, T4 is low, and there are clinical manifestations. Latent is milder: the stimulating hormone rises, but T4 is still normal. Myxedema is the extreme degree in adults; in children its analogue is called cretinism. The word means mucous swelling of the skin: puffy face, swelling around the eyes, large lips and tongue with tooth marks, hoarse voice, swollen limbs. Myxedema coma is a rare life-threatening progression, more often in the elderly, treated in hospital.

Hypothyroidism itself is not a reason to call an ambulance; 103/112 — if there is a suspicion of myxedema coma, a rare life-threatening complication of severe untreated hypothyroidism, more often in older people.

Main signs of hypothyroidism

The signs are mild and vague, develop slowly, and a person may not notice them for months and years. Pronounced fatigue, feeling cold and poor cold tolerance, weight gain, constipation, difficulty concentrating, low mood or depression, dry skin, dry and falling hair, hoarse voice, irregular or heavy periods. There may be a puffy face, muscle and joint pain, slow pulse, goiter — an enlarged gland that makes the neck look swollen and sometimes causes difficulty breathing and swallowing. Without treatment, the risk of heart and bone problems, including osteoporosis, increases, and cholesterol rises. A separate topic is gestational hypothyroidism: during pregnancy it threatens preeclampsia, preterm birth, miscarriage, and affects the child's growth and development.

How hypothyroidism is diagnosed and when to see a doctor

Diagnosis begins with a conversation: symptoms, thyroid and autoimmune conditions in the family, recent pregnancy. The doctor examines the neck and looks for an enlarged gland. Then blood tests: TSH, T4, and if needed T3 and thyroid antibodies. Sometimes ultrasound, scintigraphy, or a radioactive iodine uptake test are added, and in complex cases the patient is referred to a specialist. It makes sense to see a doctor if you recognize yourself in the list: the symptoms are nonspecific and need to be checked by a doctor. Hypothyroidism is often detected late precisely because of its subtle onset — in Russia, for example, they cite 21 cases per 1000 women and 19 per 1000 men.

This material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer