In its earliest stage, hypothyroidism may cause few symptoms, since the body has the ability to partially compensate for a failing thyroid gland by increasing the stimulation to it, much like pressing down on the accelerator when climbing a hill to keep the car going the same speed.
As thyroid hormone production decreases and the body's metabolism slows a variety of features may result, including:
- Pervasive fatigue
- Difficulty learning
- Dry, brittle hair and nails
- Dry, itchy skin
- Puffy face
- Sore muscles
- Weight gain and fluid retention
- Heavy and/or irregular menstrual flow
- Increased frequency of miscarriages
- Increased sensitivity to many medications
There are many possible causes of hypothyroidism, including:
Autoimmune Thyroiditis (Hashimoto's Thyroiditis)
The body's immune system may produce a reaction in the thyroid gland that results in hypothyroidism and, most often, a goiter (enlargement of the thyroid). Other autoimmune diseases may be associated with this disorder, and additional family members may also be affected.
Radioactive Iodine Treatment
Hypothyroidism frequently develops as a desired therapeutic goal after the use of radioactive iodine treatment for hyperthyroidism.
Hypothyroidism may be related to surgery on the thyroid gland, especially if most of the thyroid has been removed.
Lithium, high doses of iodine, and amiodarone (Cordarone, Pacerone) can cause hypothyroidism.
This condition may follow a viral infection and is characterized by painful thyroid gland enlargement and inflammation, which results in the release of large amounts of thyroid hormones into the blood. Fortunately, this condition usually resolves spontaneously. The thyroid usually heals itself over several months, but often not before a temporary period of hypothyroidism occurs.
Five percent to 10 percent of women develop mild to moderate hyperthyroidism within several months of giving birth. Hyperthyroidism in this condition usually lasts for approximately 1 to 2 months. It is often followed by several months of hypothyroidism, but most women will eventually recover normal thyroid function. In some cases, however, the thyroid gland does not heal, so the hypothyroidism becomes permanent and requires lifelong thyroid hormone replacement.
Transient (temporary) hyperthyroidism can be caused by silent thyroiditis, a condition which appears to be the same as postpartum thyroiditis but not related to pregnancy. It is not accompanied by a painful thyroid gland.
An infant may be born with an inadequate amount of thyroid tissue or an enzyme defect that does not allow normal thyroid hormone production. If this condition is not treated promptly, physical stunting and/or mental damage (cretinism) may develop.
Any destructive disease of the pituitary gland may cause damage to the cells that secrete Thyroid Stimulating Hormone (TSH), which stimulates the thyroid to produce normal amounts of thyroid hormone. This is a very rare cause of hypothyroidism.