Signs and symptoms of hypothyroidism:
• Depression
• Difficulty losing weight
• Dry skin
• Headaches
• Hyperlipidemia
• Lethargy or fatigue
• Memory problems
• Menstrual problems
• Recurrent infections
• Sensitivity to cold
• Thinning of head hair
• Voice changes
Hypothyroidism is low thyroid gland function. The thyroid gland is situated in the front of the neck, just below the larynx (voice box). Since the hormones of the thyroid gland regulate metabolism in every cell of the body, a deficiency of thyroid hormones can affect virtually all body functions. The severity of symptoms in adults ranges from very mild deficiency states that are barely detectable (subclinical hypothyroidism) to severe deficiency states that are life-threatening (myxedema).
A deficiency of thyroid hormone may be due to defective hormone synthesis or to lack of stimulation by the pituitary gland. The pituitary gland is responsible for secreting thyroid-stimulating hormone (TSH). When thyroid hormone levels in the blood are low, the pituitary secretes TSH. If a blood test shows that thyroid hormone levels are low and TSH levels are elevated in the blood, it usually indicates defective thyroid hormone synthesis. This situation is termed primary hypothyroidism.
If TSH levels are low and thyroid hormone levels are also low, this indicates that the pituitary gland is responsible for the low thyroid function. This situation is termed secondary hypothyroidism.
Using blood levels of thyroid hormones as the criterion may exclude a large number of people with mild hypothyroidism, but according to this criterion it is estimated that approximately 5 to 10% of the adult population have hypothyroidism.1–4 The Colorado Thyroid Disease Prevalence Study suggested that no less than 10% of the adult population is affected, with a rate over 20% in senior citizens.5
Overall, thyroid disease of all types is two to eight times more common among women. Hypothyroidism is more prevalent among Caucasians and Mexican Americans, with 5.7% being affected, than among African-Americans, with 1.7% affected.6
Some writers of popular books estimate that 40% of adults would be considered hypothyroid when symptoms and basal body temperature are used for diagnosis.7,8 It is likely that the true rate of hypothyroidism according to these criteria is somewhere near 25% of the adult population and significantly higher in the elderly. This makes hypothyroidism a surprisingly common, usually unrecognized condition.
The degree of severity of symptoms in adults ranges from early, mild deficiency states that are not detectable with standard blood tests (hypothyroid syndrome) to severe deficiency states that can be life-threatening (myxedema).
The brain appears to be quite sensitive to low levels of thyroid hormone. Depression, weakness, and fatigue are usually the first symptoms of hypothyroidism.9–11 Later the hypothyroid individual has difficulty concentrating and is extremely forgetful.
A lack of thyroid hormones leads to a general decrease in the rate of utilization of fat, protein, and carbohydrate. Moderate weight gain combined with sensitivity to cold weather (demonstrated by cold hands or feet) is a common finding. Hypothyroidism often results in swelling of tissue and fluid retention (edema).
Hypothyroidism, even in very mild cases, is thought to predispose people to atherosclerosis because of increases in cholesterol and triglycerides as well as homocysteine and C-reactive protein (CRP). Hypothyroidism can also cause high blood pressure, reduce the function of the heart, and reduce heart rate.9,12–14
Various hormonal symptoms can exist in hypothyroidism. Perhaps the most common is a loss of libido (sexual drive) in men and menstrual abnormalities in women. Women with mild hypothyroidism have prolonged and heavy menstrual bleeding, with a shorter menstrual cycle. Infertility may also be a problem. If a hypothyroid woman becomes pregnant, miscarriages, premature deliveries, and stillbirths are more common.
Low adrenal function is often a companion to low thyroid function, as patients with thyroid antibodies are likely to also have antibodies that attack the adrenals.
Dry, rough skin covered with fine superficial scales is seen in most hypothyroid individuals, while the hair is coarse, dry, and brittle. Hair loss can be quite severe and is generally diffuse as opposed to patchy. The nails become thin and brittle and typically show crosswise grooves.
Muscle weakness and joint stiffness are predominate features of hypothyroidism.15 Some individuals with hypothyroidism may also experience muscle and joint pain, as well as tenderness.16
Shortness of breath, constipation, and impaired kidney function are some of the other common features of hypothyroidism.
Causes
About 95% of all cases of clinical hypothyroidism are primary. Around the globe the most common cause of hypothyroidism is iodine deficiency. The thyroid gland adds iodine to the amino acid tyrosine to create thyroid hormones. Iodine deficiency leads to hypothyroidism or the development of an enlarged thyroid gland (a goiter), or both.
Goiters are estimated to affect more than 200 million people worldwide. In all but 4% of these cases, the cause is an iodine deficiency. Iodine deficiency is quite rare in the United States and other industrialized countries, owing to the addition of iodine to table salt. Adding iodine to table salt began in Michigan, where in 1924 the goiter rate was an incredible 47%. However, the incidence of deficiency has increased owing to several factors: more people eat out, in places where the salt in food is usually not iodized (many chefs believe iodizing affects the taste of food); iodine compounds are no longer used in commercial bread; and dairy products have less iodine because the udders of cows are no longer sterilized with iodine compounds. The end result is that iodine consumption has decreased 50% in the past 20 years.
Although few people in the United States are now considered iodine deficient, some still develop goiters, and many cases of mild hypothyroidism are simply not recognized. A possible cause of goiters or nodules in patients with adequate but marginal iodine intake is the excessive ingestion of goitrogens—foods that block iodine utilization. These include vegetables in the brassica family (turnips, cabbage, broccoli, brussels sprouts, mustard, kale, cauliflower), cassava root, soybeans, peanuts, pine nuts, and millet. Cooking usually inactivates goitrogens.
Environmental goitrogens include perchlorate, fluoride, and mercury. Medications that induce goiters and suppress thyroid function include supplemental iodine in excess of 1,000 mcg per day, amiodarone, carbamazepine, lithium, phenobarbital, phenytoin, and rifampin. In addition, the bromates now used in commercial bread are iodine antagonists.
Goiters can also be the result of Hashimoto’s thyroiditis, an autoimmune disorder that is the most frequent cause of clinical hypothyroidism in the United States. In this disease antibodies that bind to the thyroid prevent the manufacture of sufficient levels of thyroid hormone. In addition to binding to thyroid tissue, these antibodies may also bind to the adrenal glands, pancreas, and acid-producing cells of the stomach (parietal cells).
Hashimoto’s thyroiditis can be reasonably assumed to be present when there are signs of autoimmune thyroid disease. These can include any of the following:
• Serum antibodies against thyroid proteins such as thyroglobulin or thyroperoxidase
• Diffuse enlargement of the gland detected by physical exam, ultrasound, or CT scan
• Diffuse iodine uptake and glandular enlargement on radioiodine uptake scan
Other causes of clinical hypothyroidism include thyroid surgery and/or ablation and postpartum hypothyroidism, the last of which is a transient form of hypothyroidism that affects 5 to 10% of women in the United States.
Subclinical Hypothyroidism and Hypothyroid Syndrome
In subclinical hypothyroidism, classically defined, TSH is elevated while serum thyroid hormone levels are normal. According to this criterion, subclinical hypothyroidism is a relatively common finding, affecting 2% to 7% of adults.9 Symptoms of hypothyroidism in the absence of laboratory findings are more accurately called hypothyroid syndrome, and this condition is associated with the following:
• The presence of hypothyroid symptoms
• The absence of other explanatory diseases
• Possible functional thyroid abnormalities such as low basal body temperature or slow Achilles reflex
For clinical hypothyroidism to be diagnosed, patients with hypothyroid syndrome must also have one or more of the following objective findings:
• Suboptimal blood levels of thyroid hormones
• Abnormal thyroid antibody studies
• Abnormal findings on ultrasound
• Abnormal findings on biopsy (fine needle aspiration of the thyroid)
Many people with hypothyroid syndrome may have early Hashimoto’s disease, while some cases can be attributed to impaired thyroid hormone synthesis or conversion related to nutritional deficiencies or environmental toxins. With the growing incidence of iodine deficiency, we expect this last cause will become more commonly recognized.
Diagnostic Considerations
Screening for hypothyroidism should include a marker of thyroid regulation (TSH), markers of thyroid output (free T4, free T3), and markers of thyroid inflammation (thyroid microsomal antibody, thyroperoxidase antibody, antithyroglobulin antibody). The American Thyroid Association recommends TSH screening every five years beginning at age 35.
Normal Blood Levels of Thyroid Hormones |
|
HORMONE |
BLOOD LEVEL |
T4 |
4.8–13.2 mcg/dl |
Free T4 |
0.9–2 ng/dl |
T3 |
80–220 ng/dl |
Thyroid-stimulating hormone (TSH) |
0.35–5.50 mIU/ml |
The diagnosis of hypothyroidism by laboratory methods is primarily based on the results of total T4, free T4, T3, and TSH levels.
Before the use of blood measurements, it was common to diagnose hypothyroidism on the basis of basal body temperature (the temperature of the body at rest) and Achilles reflex time (reflexes are slowed in hypothyroidism). With the advent of sophisticated laboratory measurement of thyroid hormones in the blood, these functional tests of thyroid function fell by the wayside. The normal basal body temperature is 97.6 to 98.2°F. Instructions for taking basal body temperature are provided below.
Many consider basal body temperature a specific indicator of thyroid status. Yet it is affected by so many other variables, including adrenal function, body composition, activity levels, menstrual status, and immune function, that it has very little specificity for thyroid function. Nonetheless, it is a good general screening test that is easy to do and virtually without cost.
TAKING YOUR BASAL BODY TEMPERATURE
Your body temperature reflects your metabolic rate, which is largely determined by hormones secreted by the thyroid gland. The function of the thyroid gland can be determined by simply measuring your basal body temperature. All that is needed is a thermometer.
1. Shake down the thermometer to below 95°F and place it by your bed before going to sleep at night.
2. On waking, place the thermometer in your armpit for a full 10 minutes. It is important to move as little as possible. Lying and resting with your eyes closed is best. Do not get up until the 10-minute test is completed.
3. After 10 minutes, read and record the temperature.
4. Record the temperature for at least three mornings (preferably at the same time of day) and give the information to your physician. Menstruating women must perform the test on the second, third, and fourth days of menstruation. Men and postmenopausal women can perform the test at any time.
Basal body temperature should be between 97.6 and 98.2°F. Low basal body temperatures are quite common and may reflect hypothyroidism. High basal body temperatures (above 98.6°F) are less common but may be evidence of hyperthyroidism (see the chapter “Hyperthyroidism”).
Therapeutic Considerations
The medical treatment of hypothyroidism, in all but its mildest forms, involves the use of desiccated thyroid or synthetic thyroid hormone. Although synthetic hormones have become popular, many physicians (particularly naturopathic physicians) still prefer the use of desiccated natural thyroid, which contains all thyroid hormones, not just thyroxine. At this time, it appears that thyroid hormone replacement is necessary in the majority of people with hypothyroidism. In particular, the use of thyroid replacement is very important in patients with Hashimoto’s thyroiditis, as it achieves two objectives: it normalizes thyroid hormone levels and also decreases autoimmune processes. Either desiccated or synthetic thyroid replacement should be used in doses high enough to decrease TSH to between 0.5 and 1.5 mIU/ml. We prefer desiccated thyroid, as it may stimulate blocking antibodies to antithyroid antibodies or act as a decoy for thyroid antibodies. Some patients are found to recover from Hashimoto thyroiditis after an extended treatment time with thyroid hormone and no longer need to be maintained on replacement, but the majority will require lifelong replacement therapy.
The thyroid extracts sold in health food stores are required by the Food and Drug Administration to be thyroxine-free. However, it is nearly impossible to remove all the hormone from the gland. In other words, think of health food store thyroid preparations as milder forms of desiccated natural thyroid. If you have mild hypothyroidism, these preparations may provide enough support to help you with your thyroid problem.
Since it is important to nutritionally support the thyroid gland by ensuring adequate intake of key nutrients required in the body’s manufacture of thyroid hormone and avoiding goitrogens (see above), most health food stores’ thyroid products also contain supportive nutrients such as iodine, zinc, selenium, and tyrosine.
Thyroid hormones are made from iodine and the amino acid tyrosine. The recommended dietary intake (RDI) for iodine in adults is quite small, 150 mcg. The average intake of iodine in the United States, once estimated to be more than 600 mcg per day, is now less than half that. Vegans, especially those who are pregnant, should be careful to ensure adequate iodine intake, as their levels are typically low.
Too much iodine can actually inhibit thyroid gland synthesis. For this reason, and because the only function of iodine in the body is for thyroid hormone synthesis, it is recommended that dietary levels or supplementation of iodine not exceed 600 mcg per day for any length of time.
Zinc, selenium, vitamin E, and vitamin A function together in many body processes, including the manufacture of thyroid hormone. A deficiency of any of these nutrients would result in production of lower levels of active thyroid hormone. Low zinc levels are common in the elderly, as is hypothyroidism.17 There may be a correlation. Supplementation with zinc has been shown to reestablish normal thyroid function in hypothyroid patients who were zinc deficient, even though they had supposedly normal serum T4 levels.18
Similarly, selenium supplementation may be important, as those living in areas of the world where selenium is deficient have a greater incidence of thyroid disease.19 Of particular significance is the fact that while a selenium deficiency does not decrease the conversion of T4 to T3 in the thyroid or the pituitary, it does result in a great decrease in this conversion in other cells of the body.20 People with a selenium deficiency have elevated levels of T4 and TSH. Supplementation with selenium results in a decrease in T4 and TSH, a normalization of thyroid activity,21 and decreased thyroid antibody levels in autoimmune thyroid conditions.22 Inadequate selenium is a common nutritional deficiency.
Vitamin B2 (riboflavin), B3 (niacin), B6 (pyridoxine), and C are also necessary for normal thyroid hormone manufacture.
QUICK REVIEW
• Since thyroid hormones affect every cell of the body, a deficiency will usually result in a large number of signs and symptoms.
• Depression, weakness, and fatigue are usually the first symptoms of hypothyroidism.
• The medical treatment of hypothyroidism, in all but its mildest forms, involves the use of desiccated thyroid or synthetic thyroid hormone.
• You can support the thyroid gland by avoiding goitrogens (foods that impair the use of iodine) and ensuring adequate intake of key nutrients that are required for the manufacture of thyroid hormone.
• In very mild cases, thyroid products from a health food store may provide benefit.
DHEA is often low in hypothyroid patients and supplementation has shown benefit in the treatment of autoimmune conditions.23 Although many clinical studies have employed high dosages (100 to 200 mg per day), if there is no physician supervision we recommend much lower doses: 5 to 15 mg per day in women and 10 to 20 mg per day in men. Higher dosages require monitoring for DHEA blood levels and clinical symptoms of excess estrogen (men) or testosterone (women). As the long-term effects of DHEA administration are unknown, DHEA should be used with caution, particularly in patients at risk for developing hormone-dependent cancers.
Exercise is particularly important in a treatment program for hypothyroidism. Exercise stimulates thyroid gland secretion and increases tissue sensitivity to thyroid hormone. Many of the health benefits of exercise may be a result of improved thyroid function.
The health benefits of exercise are especially important in overweight hypothyroid individuals who are dieting. A consistent effect of dieting is a decrease in the metabolic rate as the body strives to conserve fuel. Exercise has been shown to prevent this decline.24
TREATMENT SUMMARY
Natural treatment strategies for normalizing thyroid function vary depending on whether there is an autoimmune hypothyroid condition, clinical hypothyroidism, subclinical hypothyroidism, or hypothyroid syndrome. Below are general recommendations to improve thyroid function.
The recommendations given in the chapter “A Health-Promoting Diet” are suitable, with the following caveat: the diet should be low in raw goitrogens and high in foods rich in the trace minerals needed for thyroid hormone production and activation. Goitrogens to be limited include brassica-family foods (turnips, cabbage, rutabagas, mustard greens, radishes, horseradishes), cassava root, soybeans, peanuts, pine nuts, and millet. When these foods are eaten, they should be cooked to break down their goitrogenic constituents.
We also recommend ruling out gluten sensitivity, as gluten may lead to the formation of thyroid-related autoantibodies in sensitive individuals.25
• A high-potency multiple vitamin and mineral formula as described in the chapter “Supplementary Measures”
• Key individual nutrients:
Copper: 1 to 1.5 mg per day
Iodine: 300 mcg per day
Selenium: 100 to 200 mcg per day
Zinc: 15 to 30 mg per day
Vitamin D3: 2,000 to 4,000 IU per day (ideally, measure blood levels and adjust dosage accordingly)
• Fish oils: 1,000 mg EPA + DHA per day
• One of the following:
Grape seed extract (>95% procyanidolic oligomers): 100 to 300 mg per day
Pine bark extract (>95% procyanidolic oligomers): 100 to 300 mg per day
Some other flavonoid-rich extract with a similar flavonoid content, super greens formula, or another plant-based antioxidant that can provide an oxygen radical absorption capacity (ORAC) of 3,000 to 6,000 units or higher per day
• Daily exercise, especially high-intensity activities, can stimulate thyroid function.