Free Thyroid for Dummies by Alan L. Rubin Page A

Also, if you have a condition that is associated with dry skin like eczema, or the menopause, this symptom may predominate even if you have hyperthyroidism, which tends to cause moist skin. The information here shows you what classic symptoms of thyroid problems look like, but everyone is different, and each person with the condition may show individual variations.
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    32 Part I: Understanding the Thyroid
    General functions
    Thyroid hormones cause every cell in your body to make more enzymes , the proteins that promote your metabolism as they act as the key to help certain chemical reactions take place. If you think of your body as a machine, then adding extra thyroid hormone is like pressing harder on the accelerator of a car. The result is a revving up of the machine – like going from 2,000 revolutions per minute to 4,000 or more revolutions per minute, depending on the amount of hormone added. In the same way, when more thyroid hormone is present in your body, more chemical reactions are taking place.
    Metabolism
    Your basal metabolic rate (BMR) is an overall measure of the amount of chemical reactions taking place in your body. Increased thyroid hormone may increase your BMR, or metabolism, as much as 60 to 100 per cent. Any machine that increases its activity heats up. Likewise, your body heats up when you make more thyroid hormone, and the result is a higher body temperature. At the other end of the scale, not enough thyroid hormone results in an abnormally low body temperature.
    As more metabolism takes place, more of your food intake is burned for energy, so less energy is available for storage. Your body detects the need for more energy and you get hungrier, but your faster metabolism usually more than offsets any increase in food intake. The net result is that you lose weight. However, if you take in too much extra food, you can actually gain weight.
    A scientist defines an individual’s basal metabolic rate (BMR) as the energy expended when lying in bed, at complete physical and mental rest, 12–14
    hours after last eating, in an ambient temperature of 26–30 oC. Although BMR is dependent on thyroid function, metabolism also varies depending on gender (usually higher in males), age (slows as you get older), lean body mass percentage (how much muscle you have), and nutritional status and genetic inheritance (which dictates the efficiency of your metabolism).
    The type of food you eat also plays a role as heat released during digestion (known as dietary-induced thermogenesis ) accounts for 10 per cent or more of the energy you get from different foods.
    Muscle function
    Although your muscles need thyroid hormone for proper functioning, too much of the hormone is not a good thing. Excess thyroid hormone results in muscle wasting, as muscle tissue is consumed as an emergency energy source. As you lose muscle, you become weaker. If too much thyroid hormone is present, the nerves sending signals to your muscles also show increased excitability, resulting in increased reflexes and muscle tremors.
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    Chapter 3: Discovering How Your Thyroid Works
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    Some unscrupulous diet regimes give unsuspecting people thyroid hormones to speed up their metabolism and help them lose weight. Although this tactic sounds like a good idea, it definitely isn’t. An overabundance of thyroid hormone results in muscle loss, so the weight you lose is not fat but muscle, the so-called lean tissue of the body. You do not want to lose lean tissue, as this loss makes you less fit, says goodbye to a toned silhouette, and increases your general flabbiness. Do not use thyroid hormone in an attempt to lose weight.
    Energy sources
    As well as affecting the protein found in muscle, thyroid hormone also affects the other sources of energy in your body, namely carbohydrates and fats.
    Carbohydrates are the main source of immediately available energy in the body, so they