Free Thyroid for Dummies by Alan L. Rubin Page B

get used up faster than normal when thyroid hormone levels rise, again resulting in more heat production. Fat is also used up faster than normal. The result is a lowering of the different kinds of fat in the body, namely cholesterol and triglycerides. On the other hand, when thyroid hormone levels drop, the fats accumulate in the liver and the level of cholesterol in the blood rises.
    Because chemical reactions require vitamins, minerals, and trace elements, your need for these substances increases when you have more thyroid hormone. Increased thyroid hormones cause a more rapid breakdown of the vitamins. However, multivitamin and minerals supplements have little effect upon the thyroid gland itself, except for those products that contain iodine (often in the form of kelp or seaweed). Supplements and foods containing iodine are best avoided when you have hyperthyroidism or multinodular goitre (see Chapter 9) where extra iodine is used to make too much thyroid hormone.
    Specific functions
    Every organ in your body requires thyroid hormone to work normally. When that hormone is lacking, the organ tends to carry out less of its usual function, and when too much thyroid hormone is present, the organ does more than it should. In this section, we discuss the most important changes due to abnormal amounts of thyroid hormone in your body. This discussion is not complete by any means, as that needs a large book in itself, and many of the changes that occur are too subtle to result in signs or symptoms that are detectable.
    The heart
    Your heart needs T4 thyroid hormone for proper pumping. If not enough T4
    is present, your heart slows down and its pumping action decreases. This 07_031727 ch03.qxp 9/6/06 10:45 PM Page 34
    34 Part I: Understanding the Thyroid
    state can even result in heart failure when T4 is severely lacking. Conversely, when T4 levels rise too high, the heart beats too rapidly. While the heart pumps out more blood at first, if this increased pumping continues for too long, it can lead to decreased heart strength so the heart pumps out less blood than normal. This problem occurs because excessive T4 causes muscle wasting, and your heart, of course, is made of muscle.
    Depending on your level of physical activity, your normal resting heart rate is usually between 60 and 80 beats per minute (assuming that you’re not taking any drugs that affect your pulse). Someone who is in exceptionally good physical condition, such as a trained athlete, may have a heart rate in the 50s or below. People with too much T4, however, often have a heart rate of 120 or faster.
    The lungs
    As your metabolism increases, you need more oxygen so that the chemical reactions in your body can take place. Oxygen comes into your body through the lungs. Your respiration rate, normally about 16 breaths per minute, has to speed up to bring in more oxygen if you have an overactive thyroid gland.
    However, even an increased respiration rate may fail to provide you with enough oxygen if your muscular diaphragm and chest muscles are wasting from excess T4.
    The stomach and intestines
    Your stomach and intestines are linked with muscles that need T4 to push food along for digestion and excretion. When not enough T4 is present, intestinal movement slows, as does the rate at which you absorb nutrients from your food. And slowed bowel movements lead to – yes, you’ve guessed it – constipation. On the other hand, having too much T4 on board speeds up your bowels, which become looser, more frequent, and can lead to diarrhoea.
    Great.
    The skin, hair, and nails
    The increased blood flow that results from a raised level of T4 is especially prominent in the skin. People with hyperthyroidism often have skin that feels warm, they may look flushed, and perspiration may increase, so it also feels moist. When T4 levels fall, the skin is more likely to feel dry and scaly and feels cold to the touch. The nails don’t achieve their proper toughness without enough