Common Name/Other Name
Underactive thyroid disease (Eng.)
Hypothyroidism is a condition where the thyroid gland does not produce thyroid hormones in adequate quantities. Older women are more commonly affected with hypothyroidism. Symptoms of hypothyroidism develop slowly. Most of the symptoms may not be noticeable or only dismissed as signs of aging.
The thyroid gland produces the hormones triiodothyronine (T3) and thyroxine (T4). These hormones affect the metabolism of the body. It maintains the metabolism of carbohydrates and fats, controls the body temperature, affects the heart rate and regulates protein synthesis. Therefore, the deficiency of thyroid hormones leads to an imbalance in most chemical reactions of the body.
There are several factors that can cause hypothyroidism:
- Autoimmune disease. Hashimoto’s thyroiditis is a common cause of hypothyroidism. It is a condition where the thyroid gland attacked by the immune system leading to inflammation.
- Treatment for hyperthyroidism. Patients who produce an excess of the thyroid hormones are treated with anti-thyroid medications. However, these medications can significantly decrease the levels of thyroid hormones and lead to hypothyroidism.
- Thyroid surgery. Removal of a part or whole thyroid gland decreases or completely stops thyroid hormone production.
- Radiation therapy. Cancers of the head and neck treated by radiation can develop hypothyroidism.
- Medications. Certain drugs for other diseases can affect the production of thyroid hormones. An example is the use of lithium for bipolar disorder.
- Congenital disease. There are babies born with a defective thyroid gland that fails to function normally. Some babies are born with no thyroid gland at all. Hypothyroidism can also be inherited by the baby. Patients suffering from congenital hypothyroidism usually appear normal at birth so the condition is not detected unless screened for it specifically.
- Pituitary gland disorder. A benign tumor in the pituitary gland can result in the reduced production of the thyroid-stimulating hormone (TSH).
- Pregnancy. During or after pregnancy, a woman might produce antibodies against its own thyroid gland. An untreated hypothyroidism increases the risk of miscarriage, premature delivery and preeclampsia.
- Iodine deficiency. An adequate intake of iodine usually found in seafood is important for the normal production of thyroid hormones. The body cannot produce iodine so it has to be supplied by diet. There are cases wherein excess iodine also led to hypothyroidism.
Diagnosis of hypothyroidism is based on the presented symptoms and results of blood test. Hypothyroidism manifests with low level of thyroxine (T4) and high level of TSH. The pituitary gland produces more TSH in response to the low levels of thyroid hormones, but the thyroid gland fails to normalize its hormone production. The TSH test is the better screening test than the thyroid hormone test. Some people have subclinical hypothyroidism which presents only with an increase in TSH level.
Cold intolerance or increased sensitivity to cold
Slow heart rate
Forgetfulness, slow thought process
Symptoms of myxedema:
Low blood pressure
Decreased body temperature
Symptoms of congenital hypothyroidism:
Jaundice or the yellowing of the skin and whites of the eyes
Large, protruding tongue
Poor muscle tone
Additional symptoms in children and teens:
Poor growth, short stature
Delayed permanent teeth development
Poor mental development
- Sex and age. Women older than 60 years old
- Family history of thyroid disease
- Autoimmune disease. Hashimoto’s thyroiditis, rheumatoid arthritis, lupus
- Treatment with anti-thyroid medications
- Radiation therapy
- Thyroid surgery
- Pregnancy. Pregnant or delivered a baby for the past 6 months
Since the thyroid hormones affect various metabolic processes in the body, untreated hypothyroidism leads to several complications:
- Goiter. The thyroid gland becomes larger when there is constant stimulation to release the hormones. This occurs when there is hypothyroidism and the body tries to signal the thyroid gland to produce more hormones. It alters the appearance of the neck and can interfere with breathing or swallowing.
- Myxedema. Myxedema is a result of a long-term untreated hypothyroidism. It presents with severe cold intolerance and drowsiness. These are followed by lethargy and loss of consciousness. Myxedema coma is a fatal complication wherein the breathing slows down, blood flow to the brain decreases and seizures occur. It can be triggered by physical stress, infection, injury, surgery and drugs that depress the brain function.
- Heart problems. The levels of the low-density lipoprotein (LDL) increase with the decrease of thyroid hormones. This will impair the functions of the heart and lead to an enlarged heart or heart failure.
- Mental health issues. Low thyroid hormone levels cause an impaired mental functioning such as forgetfulness. Depression is one of the symptoms of hypothyroidism. It can progress throughout the duration of the disease.
- Peripheral neuropathy. The nerves that carry the signal from the brain and spinal cord to other parts of the body are damaged when there is a long-term condition of hypothyroidism. The patient feels pain, numbness and tingling on the affected area such as the arms and legs.
- Infertility. Deficiency in thyroid hormones disturbs normal ovulation which can cause infertility.
- Birth defects. If the pregnant woman delivers a child when she has untreated hypothyroidism, the baby might have birth defects and develop intellectual problems. If the hypothyroidism of the infant is left untreated, he/she might develop severe physical and mental retardation.
Commonly Prescribed Drugs
- Levothyroxine. Levothyroxine is a synthetic oral preparation of T4 that returns the thyroid hormone levels to its normal state. This is given on a daily basis and may be lifelong. The dose is started low and adjusted until the TSH levels are in the midnormal range. Levothyroxine is given intravenously for myxedema coma.
- Liothyronine. Liothyronine, a synthetic preparation of T3 is not used for long-term replacement of thyroid hormones. It has a short half-life and rapidly increases the T3 levels in the body. This causes the patient to have a hyperthyroid for several days and increased risk for cardiac problems.