Hyperthyroidism (too much hormone) may cause inexplicable weight loss, heart palpitations, nervousness, irritability, diarrhea, moist skin, muscle weakness, and a startled appearance of the eyes. You may also experience hair loss as metabolism speeds up. Hyperthyroidism is much less common than hypothyroidism and affects about 1 percent of the US population.
The tests: A blood test measures thyroid-stimulating hormone, which is produced by the pituitary gland in an attempt to coax the thyroid to make thyroid hormone. Excess TSH usually indicates hypothyroidism, while abnormally low levels suggest hyperthyroidism.
What you can do: Your doctor may prescribe a thyroid hormone medication to restore levels to normal. Regular TSH tests might be done to ensure an adequate dosage.