An estimated 5 percent of the population of the United States has a thyroid gland that functions poorly, a condition called hypothyroidism, the National Endocrine and Metabolic Diseases Information Services reports. This thyroid disease can cause a number of symptoms in affected people, including symptoms that mimic the flu. People who experience flu-like hypothyroidism symptoms, especially women over the age of 60, should have their thyroid hormone levels checked by a medical professional.
Excessive fatigue or sluggishness may occur as a flu-like symptom associated with hypothyroidism. Low thyroid hormone levels in the body cause a decrease in the body's normal metabolism. When the body can't break down energy supplies quickly, the organs, tissues and cells in the body don't receive the fuel necessary to support a person's normal physical energy demands. People who experience increased fatigue may have difficulty remaining attentive or focused throughout the day or may take frequent naps in order to remain energized.
Muscle or Joint Pain
Unusual sensations of pain may arise in the muscles or joints of people with hypothyroidism, MayoClinic.com warns. The affected joints may appear swollen, puffy or discolored and can be warm to the touch. Body discomfort may exacerbate fatigue symptoms and may make it difficult for people with this thyroid disease to move about normally.
Increased sensitivity to cold temperatures is a common symptom of hypothyroidism. Affected people may frequently experience chills or may feel abnormally cold in warm or temperate environments.
Additional symptoms associated with hypothyroidism include weight gain, swelling of the face or eyes, dry skin, vocal hoarseness, constipation, brittle or dry hair or fingernails, depression or decreased heart rate. People with low thyroid hormone levels may also be at risk of developing high levels of cholesterol in the blood. Additionally, women with this condition may experience irregular or unusually heavy menstrual cycles or may have trouble becoming pregnant.