- Muscle weakness
- Elevated blood cholesterol level
- Muscle aches, tenderness, and stiffness
- Pain, stiffness, or swelling in your joints
- Heavier than normal or irregular menstrual periods
- Thinning hair
- Slowed heart rate
- Depression
- Impaired memory
- Enlarged thyroid gland (goiter)
These symptoms usually develop over a number of years and may be attributed to other health concerns or age, making hypothyroidism slightly more difficult to catch and treat. One may develop hypothyroidism for a number of reasons including:
Hashimoto's thyroiditis - Hashimoto's thyroiditis is an autoimmune disease where the immune system produces antibodies that attack the thyroid gland and cause swelling and inflammation. The thyroid gland then produces less T3 and T4, leading to hypothyroidism.
Thyroid surgery- Some individuals need to have part of or all of the thyroid gland removed, thus preventing the gland from producing the necessary thyroid hormones. These individuals often have to take supplemental hormones for the rest of their life.
Radiation treatments - According to the Mayo Clinic, "radiation used to treat cancers of the head and neck can affect your thyroid gland and may lead to hypothyroidism."
Certain medications - Certain medications such as lithium have been linked to low levels of hormones being produced by the thyroid gland.
Over-response to hyperthyroidism treatment - Sometimes those with hyperthyroidism are given radioactive iodine or anti-thyroid medications to slow the overproduction of thyroid hormones. After the thyroid returns to normal, however, treatment can go too far and permanently cause hypothyroidism.
If you believe that you are experiencing signs or symptoms of a thyroid problem, talk to your doctor about getting tested and possible treatment options. They will likely order a blood test to test for thyroid hormones levels in the blood. This test is referred to as a thyroid function test, and tests for both thyroid-stimulating hormone (TSH) and thyroxine in the blood. According to the National Health Service, "A high level of TSH and a low level of T4 in the blood could mean you have an underactive thyroid. If your test results show raised TSH but normal T4, you may be at risk of developing an underactive thyroid in the future."