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Patient Story

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A 6-week-old girl, who was born at home and was not screened at birth for congenital hypothyroidism, presented to her pediatrician with signs of jaundice and was found to be hypothyroid with an elevated TSH (Figure 191-1). She was started on levothyroxine and her dose was titrated until her TSH was normal. At her 1 year old visit she was a normal healthy child with a normal developmental exam.

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FIGURE 191-1

Congenital hypothyroidism in a 6-week-old girl with signs of jaundice and an elevated TSH. (Used with permission from the CDC/Dr. Hudson.)

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Introduction

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  • Hypothyroidism is a condition caused by lack of thyroid hormone and usually develops as a result of thyroid failure from intrinsic thyroid disease. The most common cause of nonendemic goitrous hypothyroidism in both children and adults is chronic lymphocytic (Hashimoto) thyroiditis, also called autoimmune thyroiditis.1

  • Congenital hypothyroidism (CH) is decreased or absent thyroid function and thyroid hormone production that is present at birth. Historically this was due to lack of iodine. In iodine-replete countries, most cases of CH are caused by defects in embryonic development (e.g., congenitally absent, underdeveloped, or ectopic thyroid gland). Other causes include inherited enzymatic defects in the synthesis of thyroxine (T4), prematurity, and anti-thyroid drugs taken during pregnancy.

  • Goiter is a spectrum of changes in the thyroid gland ranging from diffuse enlargement to nodular enlargement depending on the cause. In the US, the most common cause of goiter with normal thyroid function or transient dysfunction is thyroiditis.

  • Subclinical thyroid disease refers to a patient with no or minimal thyroid-related symptoms but abnormal laboratory values (elevated TSH and thyroxine level within the normal range).

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Epidemiology

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  • Based on a population study in Scotland, the prevalence of hypothyroidism in children (<22 years of age) is 0.135 percent; the prevalence is 0.113 percent in children aged 11 to 18 years.2 These values are twice those of previous estimates. The most common cause of acquired hypothyroidism was autoimmune disease.

  • CH occurs in about 1 per 3000 to 4000 births in the US with a female to male ratio of 2: 1. It is the most preventable cause of cognitive impairment in children.3 There is a higher incidence of CH in some ethnic groups such as Greek Cypriots (1 per 1800) and Asians (1 per 918 in Northern England).4,5

  • In a New Zealand population study, the overall incidence of CH rose from 2.6 to 3.6 per 10,000 live births over an 18-year period thought to be due to a shift in population with proportionately more Asian and Pacific Island births.6

  • Worldwide, goiter is the most common endocrine disorder with rates of 4 to 15 percent in areas of adequate iodine intake and more than 90 percent where there is iodine deficiency.7 Endemic goiter is defined as goiter that affects more than 5 percent of the population (...

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