Doctor's Notes on Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormone, which affects the body’s metabolic processes. Low thyroid hormone levels decrease metabolism, and increase the risk of other health issues such as heart disease and pregnancy problems. Common causes of hypothyroidism in adults include autoimmune thyroiditis (Hashimoto's thyroiditis), subacute thyroiditis (inflammation of the thyroid gland after a viral disease or after a pregnancy), previous thyroid therapy, drug-induced hypothyroidism, pituitary and hypothalamic disease, and iodine deficiency.
Symptoms of hypothyroidism include fatigue, weakness, cold intolerance, muscle aches and cramps, constipation, weight gain or difficulty losing weight, poor appetite, goiter (enlarged thyroid gland), dry and rough skin, coarse hair or hair loss, eye and face swelling, deeper and/or hoarse voice, enlarged tongue, irregular or heavy menstrual periods, depression, memory loss, slowed thinking and mental activity, or increased blood cholesterol levels.
Symptoms and signs of hypothyroidism and their degree of severity may vary and depend on the duration and extent of thyroid hormone deficiency. Individuals with hypothyroidism may experience:
- Intolerance to cold
- Muscle aching and cramps
- Weight gain or difficulty losing weight
- Poor appetite
- Goiter (enlarged thyroid gland)
- Dry, rough skin
- Coarse hair or hair loss
- Eye and face swelling
- Deeper and/or hoarse voice
- Enlarged tongue
- Irregular or heavy menstrual periods
- Memory loss
- Slowed thinking and mental activity
- Increased blood cholesterol levels
Common causes of hypothyroidism in adults include:
Autoimmune Thyroiditis (Hashimoto's Thyroiditis)
This inherited condition is the most common cause of hypothyroidism in adults. Hashimoto's thyroiditis is an autoimmune disease in which the body's immune system, or natural defense system, attacks its own thyroid gland. This causes a thyroid enlargement or goiter and progressive thyroid destruction.
Subacute Thyroiditis (inflammation of the thyroid gland after a viral disease or after a pregnancy)
In this condition there is usually a phase of hyperthyroidism (a condition in which the thyroid produces an excess of thyroid hormones) followed by a hypothyroid phase. Eventually thyroid function returns to normal. The three types of subacute thyroiditis are:
- subacute granulomatous thyroiditis, also referred to as painful thyroiditis;
- subacute painless thyroiditis, which is silent and also referred to as lymphocytic thyroiditis; and
- postpartum thyroiditis.
Previous Thyroid Therapy
Surgical removal of the thyroid gland may be performed to treat thyroid nodules, hyperthyroidism, or other conditions. Treatment of hyperthyroidism with radioactive iodine also results in destruction of thyroid tissue and may lead to hypothyroidism.
Pituitary and Hypothalamic disease
Both the hypothalamus and pituitary gland are involved in the signaling pathways that control the function of the thyroid gland. Diseases of the hypothalamus and pituitary gland can, therefore, affect the amount of thyroid hormone made and secreted by the thyroid gland. Hypothyroidism due to pituitary disease is termed "secondary hypothyroidism," while hypothyroidism due to hypothalamic disease is termed "tertiary hypothyroidism."
Iodine deficiency does not occur in the U.S.. Only severe iodine deficiency will cause low thyroid hormone levels. This condition may occur in mountainous areas of poor, less industrialized nations. Mild to moderate iodine deficiency is common in many European countries.
It's hard to tell if you have thyroid abnormalities. You might feel run down and tired, or have what is known as "brain fog." You may be gaining weight, pregnant, or experiencing hair loss. Others may feel "hyper," anxious, or sweat a lot more than usual. All of these are common symptoms of thyroid disorders. The thyroid gland regulates many processes within the body, and women are particularly likely to have disorders that affect the function of this essential gland. Recognizing and treating these conditions is critical for optimum health and preventing long-term health problems.
Thyroid : Test Your Medical IQ QuizQuestion
Where is the thyroid gland located?See Answer
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.