Normal thyroid function tests

Dear Ask The Doctor: Hi, I've got some questions regarding low thyroid. Some family history. My mother and older sister have been diagnosed with low thyroid and my younger sister has been diagnosed with hyperthyroid. Both of my sisters have been diagnosed with Chron's. My symptoms: - chronic constipation (almost 20 years). Seeing a GI specialist and she is about done running all of the usual tests and everything looks OK and normal. Calling it functional constipation. - low heart rate. When this was noticed (at time measured below 40 bpm and can regularly sit at resting in low 40's), went to a cardiologist and had all the tests done. The heart was found to be normal, just a low resting heart rate. - sleep apnea. Went to see a sleep specialist and they've put me on a CPAP machine. Sleeping much better with the machine. - fatigue - very little energy - weight gain - when this started in my early 20's I was in very good shape and a healthy 215-220lbs (6'2" and a big frame). I've gain weitght constantly since this started and weigh about 280. This is high for me but it has usually been around 260. - very active with gym, biking, walking and playing hockey but have a very difficult time losing weight. My doctory as checked my blood levels several times for thyroid hormone levels and they've come back normal every time. I'm at a loss to explain what is happening and would like to have some ideas as to what questions I should be asking and what some next steps might be. I've read where you can have a low thyroid and blood levels look normal. Any insight you can give would be helpful. Dave

Dear David:Thyroid function tests include a Thyroid Stimulating hormone (TSH) level and thyroid hormone (T4) level. TSH does exactly as the name suggests, it stimulates the thyroid gland to produce the hormone thyroxine. If you suffer from hypothyroidism your thyroid gland is underactive and cannot produce enough thyroxine to meet the body's requirements. Therefore your TSH level will be high, because more TSH will be released to try and stimulate your thyroid gland to produce adequate thyroid hormone for your body's specific requirements. If your thyroid function tests are all within the normal range, you do not have hypothyroidism. I suggest you attend your family physician to find an alternative diagnosis for your symptoms