Subclinical hypothyroidism—also called mild thyroid failure—is a disease in which patients have an underactive thyroid. The primary cause of this condition is a disorder of the thyroid gland. These patients typically have significantly elevated levels of thyroid stimulating hormone (TSH), but normal levels of free thyroxine (T4) in the blood. Subclinical hypothyroidism is a relatively common syndrome that affects nearly 10 million people in the United States alone. This condition occurs most frequently in elderly women and can be difficult to detect in the absence of a blood test, as external symptoms are typically infrequent. If left untreated, subclinical hypothyroidism may progress to overt hypothyroidism, which carries with it an increased risk of elevated cholesterol levels and cardiac dysfunction. Though the majority of individuals with subclinical hypothyroidism do not exhibit notable symptoms independent of elevated TSH levels, symptoms of this condition may vary based upon the extent of hormone deficiency.
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If you have subclinical hypothyroidism, the decreased levels of thyroid hormone within your blood can lead to a number of symptoms that are apparent throughout your body. You may find that you grow tired more easily or do not have the same level of energy you used to experience. You may be more sensitive to temperature changes—especially cold temperatures. Your muscles or joints may become painful or you may find it difficult to lift items you once had no problem handling. Despite maintaining a healthy diet and exercising, you may find that you experience unexplained weight gain, which may make your face appear bloated and puffy. Some individuals also exhibit elevated cholesterol levels in the blood.
Skin, Hair or Nail Symptoms
If you have subclinical hypothyroidism, decreased thyroid hormone levels can affect the appearance of your skin, hair or nails. You may find that your skin becomes dry and flaky, and your skin may take on a pale or yellowish appearance. Your hair and nails may become dry and brittle, causing either to break easily.
If you have subclinical hypothyroidism, low levels of thyroid hormones may lead to psychological symptoms. You may develop depression, which may leave you feeling tired, irritable, restless or uninterested in your normal activities.
Females with subclinical hypothyroidism may experience additional symptoms. Decrease thyroid hormone levels may cause you to experience exceptionally heavy menstrual periods.