The bones Your bones lose calcium and become less dense, especially if you’re past menopause and aren’t taking estrogen. Despite loss of bone density and calcium, bone fractures aren’t common in hyperthyroid patients. When your doctor measures your blood calcium, it’s elevated, but kidney stones don’t occur. All bone changes return to normal with treatment of your hyperthyroidism.
The urinary system As more blood flows, your kidneys filter more, and your body produces more urine, so you go to the bathroom more frequently. In turn, you feel thirstier than usual.
Confirming a Diagnosis of Hyperthyroidism The signs and symptoms I describe in the previous section usually lead to a conclusive diagnosis of hyperthyroidism, which blood tests confirm. The definitive tests for hyperthyroidism are as follows: Free thyroxine (FT4) level: The levels of free T4 in your blood are elevated. Thyroid-stimulating hormone (TSH) level: The thyroid-stimulating hormone (TSH) level is suppressed (see Chapter 4). Other tests that support the diagnosis include Total T3 and Free T3 levels: Less than 5 percent of patients with hyperthyroidism have a normal free T4 but an elevated total T3 and free T3, a condition called T3 thyrotoxicosis, which behaves just like T4 thyrotoxicosis. T3 thyrotoxicosis can be a source of confusion when the patient has all the symptoms of hyperthyroidism but has a normal T4. The TSH is still low in cases of T3 thyrotoxicosis. Thyroid autoantibody levels: If Graves’ disease is the cause of hyperthyroidism, the levels of peroxidase autoantibody and antithyroglobulin autoantibody are elevated (see Chapter 4). They decline when the treatment is antithyroid drugs (see the “Antithyroid pills” section later in the chapter) but not when the patient receives radioactive iodine. Blood glucose level: Your blood glucose (sugar) level is elevated, because your body is absorbing food so rapidly. You may have insulin resistance, and your doctor may find that you have diabetes or that it’s worsening if insulin resistance is already present. (Diabetes improves after you receive treatment for your hyperthyroidism.) Liver function tests: Blood tests of your liver function (such as the alkaline phosphatase