Who Develops Hypothyroidism?
Select a category from the list or scroll down the page.
• Age and Gender
• Genetic Defects
• Smoking in Women with Hypothyroidism
• Risk Factors for Pregnant Women
• Other Risk Factors

Age and Gender
Estimates suggest that almost 1 in 10 Americans, approximately 27 million people, have a thyroid disorder.¹ Thyroid disease strikes women more often than men.² The elderly are the most susceptible to hypothyroidism.³ Underdiagnosis is a risk in the elderly because many of the symptoms of hypothyroidism-dry skin, fatigue, constipation, and memory loss-may be mistaken for signs of aging.⁴

However, hypothyroidism can affect people of all ages, and 1 out of every 3,500 infants is born without a thyroid gland.⁵ Hashimoto's thyroiditis-an inflammation of the thyroid caused by autoimmune factors-is the leading cause of hypothyroidism, affecting about 14 million Americans, and is 7 times more common in women than in men.^{2
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Genetic Defects
Heredity plays a role in both underactive and overactive thyroid; about half of those with close relatives with chronic autoimmune disease have antibodies-the immune system's agents for attacking specific proteins-to the thyroid. Approximately one third of those with Turner syndrome-one of the most common genetic diseases in women-have a thyroid disorder, usually hypothyroidism, in most cases resulting from Hashimoto's thyroiditis.^{5
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Smoking in Women with Hypothyroidism
Smoking is generally regarded as an unhealthy habit for many reasons, and in women with hypothyroidism, it should likewise be avoided. In a study reported in The New England Journal of Medicine, women with subclinical hypothyroidism who also smoked had higher total LDL cholesterol levels than nonsmokers. Women with hypothyroidism who smoked also had higher serum cholesterol concentrations and more muscle problems than those who did not smoke.⁶ It was concluded that smoking impairs both thyroid hormone secretion and thyroid hormone action. Therefore, your smoking status needs to be considered when hypothyroidism is suspected or being medically managed.
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Risk Factors for Pregnant Women
Thyroid dysfunction can have harmful effects on the fetus and the mother during pregnancy.^10-14 The NIH (National Institutes of Health) has also established that untreated hypothyroidism during pregnancy can adversely affect the IQ of children.^{15
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Other Risk Factors
Hypothyroidism occasionally occurs with Addison's disease, pernicious anemia, insulin-dependent diabetes, Sjogren’s syndrome, and rheumatoid arthritis.¹⁶ It is also associated with myasthenia gravis, ovarian failure, sleep apnea, and premature gray hair.⁹ Physicians should check for hypothyroidism in older people with any of these conditions.

People with anorexia or bulimia are also at risk for hypothyroidism; in these cases, however, reduced thyroid function may be an adaptation to malnutrition, and, therefore, some experts think only the eating disorder should be treated, not hypothyroidism. Women who have hypothyroidism are also at greater risk for autoimmune conditions.^4,9

Since many drugs affect the thyroid, anyone being treated for a chronic disease, anyone who is taking thyroid medication and requires other drugs, or anyone who is at risk for thyroid disorder and needs to take medications should discuss with their physician the impact of the particular drug on their thyroid.

If you believe you may have symptoms of hypothyroidism, see a physician; only a physician can diagnose hypothyroidism.
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1. Goolsby MJ, Blackwell J. Evaluation and treatment of hyperthyroidism and hypothyroidism. J Am Acad Nurse Pract. 2004; 16 (10):422–425.
2. Hypothyroidism. In: Berkow R, ed. The Merck Manual of Diagnosis and Therapy. 16th edition. Rahway, NJ: Merck Research Laboratories; 1992:1082-1083.
3. Coll PP, Abourizk NN. Successful withdrawal of thyroid hormone therapy in nursing home patients. J Am Board of Fam Pract. 2000;13(6):403-407.
4. Endocrinology and Metabolism. In: Isselbacher KJ, Braunwald E, Wilson JD, Martin JB, Fauci AS, Kasper DL, eds. Harrison’s Principles of Internal Medicine. 13th ed. New York, NY: McGraw-Hill, Inc.;1994:1940.
5. Thyroid Foundation of America. The most common problem—Hypothyroidism. Available at: http://www.tsh.org/disorders/hypthyroidism/hypothyroidism.html. Accessed April 5, 2007.
6. Hashimoto’s Thyroiditis: Information for Patients. Jacksonville, Fla: American Association of Clinical Endocrinologists; 2005.
7. National Institutes of Health. Turner syndrome website. Available at: http://turners.nichd.nih.gov/ClinFrIntro.html. Accessed April 26, 2007.
8. Muller B, Zulewski H, Huber P, Ratcliffe JG, Staub JJ. Impaired action of thyroid hormone associated with smoking in women with hypothyroidism. N Engl J Med. 1995;33(15):964-969.
9. Arem R. The Thyroid Solution. 1st ed. New York, NY: Ballantine Books; 2000.
10. Leung AS, Millar LK, Koonings PP, et al. Perinatal outcome in hypothyroid pregnancies. Obstet Gynecol. 1993;81:349-353.
11. Glinoer D, Fernandez Soto M, Bourdoux P, et al. Pregnancy in patients with mild thyroid abnormalities: maternal and neonatal repercussions. J Clin Endocrinol Metab. 1991;73:421-427.
12. Glinoer D, Riahi M, Grun J-P, et al. Risk of subclinical hypothyroidism in pregnant women with asymptomatic autoimmune thyroid disorders.
    J Clin Endocrinol Metab. 1994;79:197-204.
13. Davis LE, Lucas MJ, Hankins GDV, et al. Thyrotoxicosis complicating pregnancy. Am J Obstet Gynecol. 1989;160:63-70.
14. Davis LE, Leveno KJ, Cunningham FG. Hypothyroidism complicating pregnancy. Obstet Gynecol. 1988;72:108-112.
15. National Institutes of Health. Hypothyroidism during pregnancy linked to lower IQ for child. Available at: http://www.nih.gov/news/pr/aug99/nichd-18.htm. Accessed June 27, 2001.
    
16. Hypothyroidism. In: Berkow R, ed. The Merck Manual of Diagnosis and Therapy. 16th edition. Rahway, NJ: Merck Research Laboratories; 1992:933-935.