Medical self-help websites, such as WebMD, Mayo Clinic, Healthline and Cleveland Clinic, provide symptom lists for low thyroid hormone levels, or hypothyroidism. Symptoms vary according to the individual and tend to develop slowly over time, and they include fatigue, lethargy, cold sensitivity, depression and muscle weakness, according to Healthline.
Hypothyroidism occurs when the thyroid gland, which produces hormones that control how the body uses energy, does not make enough thyroid hormone, notes WebMD. Although it can afflict people of any age, older adults are more prone to be affected, with women age 60 and over carrying the highest risk. Left untreated, the condition can affect the entire body, including raising cholesterol levels or potentially harming a baby during pregnancy.
Failure of the thyroid to produce appropriate levels of hormones has several causes, including autoimmune disease, which occurs when immune system antibodies attack body tissues; treatment of hyperthyroidism, which can lead to permanent hypothyroidism; thyroid removal surgery, which lessens or stops hormone production; and certain medications that can lead to hypothyroidism, explain Mayo Clinic. Other potential factors include congenital disease, pituitary disorder, pregnancy and iodine deficiency. Hypothyroidism treatment requires the regular use of levothyroxine, a synthetic thyroid hormone, which helps return hormone levels to normal and alleviates accompanying symptoms.