The thyroid is a small gland found in the neck that affects food and energy metabolism. According to the Cleveland Clinic, more than 20 million Americans have a thyroid disease, and it affects more women than men. Thyroid problems may cause hypothyroidism (underactive thyroid), in which the thyroid gland produces too few hormones, or hyperthyroidism (overactive thyroid), in which it produces too many. Symptoms generally dissipate with proper treatment.
Weight Gain or Weight Loss
Because the thyroid gland affects food and energy metabolism, thyroid problems commonly cause increases or decreases in body weight. According to the American Thyroid Association, weight gain caused by hypothyroidism is generally modest and a product of salt and water buildup as well as slight decreases in the body's metabolism. Hypothyroidism also may cause lethargy, so you may gain weight as a result of reduced activity.
Hyperthyroidism may have the opposite effect, contributing to weight loss. Such weight loss may occur suddenly, regardless of your food intake. Because sudden weight loss can indicate a variety of conditions, some life-threatening, seek medical guidance promptly if it occurs.
Lethargy or Anxiety
Hypothyroidism frequently causes reduced energy and lethargy. People with the condition may complain of feeling "sluggish" or have difficulty getting out of bed in the morning. According to the Cleveland Clinic, these symptoms occur because the body responds to thyroid deficiency by using its energy slower than it should.
Hyperthyroidism, on the other hand, causes the body to use its energy faster than it should. As a result, people with the condition often experience anxiety or increased irritability. If you have an overactive thyroid, you may experience symptoms similar to those caused by excessive caffeine intake--uncomfortably edgy and as though you do not have patience to sit still or demonstrate patience.
Menstrual Irregularities
The thyroid gland affects hormones involved with a woman's menstrual cycle. Women with hypothyroidism may experience heavy, frequent menstruation. According to the Mayo Clinic, heavy menstruation, or menorrhagia, also can indicate numerous other medical conditions, such as dysfunctional ovaries, uterine fibroids (non-cancerous tumors), polyps (non-cancerous growths) and pregnancy complications.
Overactive thyroid can cause women to experience infrequent or light periods, which may be mistaken for symptoms of menopause, if it occurs during middle-age, or as a side effect weight loss or stress. If you experience menstrual irregularities, discuss all of your symptoms with your doctor.
Sensitivity to Heat or Cold
Thyroid problems can affect a person's ability to regulate temperature properly. Hypothyroidism commonly causes increased sensitivity to cold. You may feel the need to wear additional clothing layers or to add extra blankets to your bed at night, even when temperatures are moderate.
Hyperthyroidism often causes heat sensitivity. You may sweat more frequently than usual or wish to turn on the air conditioner. Women experiencing menopause or perimenopause may mistake thyroid-related heat sensitivity for hot flash symptoms. Keep in mind that hot flashes arise suddenly, while general heat sensitivity may persist steadily, whenever heat is present.
