Healthy number: A thyroid-stimulating hormone level under 4.0 mIU/L.
Produced by the pituitary gland, the thyroid-stimulating hormone (TSH) directs the thyroid gland in your neck to secrete the hormones thyroxine (T4) and triiodothyronine (T3). Besides helping regulate your metabolism, body temperature, and heart rate, these hormones affect skin, hair, muscle strength, mood, and mental functioning. If your TSH level is high, above 4.5 mIU/L (or milli–international units of TSH per liter of blood), your thyroid isn’t producing enough hormones to help your body function efficiently.
Have yours checked: Starting at age 35. Hypothyroidism is a condition that is fairly common among women and can raise cholesterol and triglyceride levels and lead to heart problems and depression. If your TSH level is high, your doctor may prescribe a thyroid replacement medication. If it is normal, recheck it every five years.