Hypothyroidism that occurs after the neonatal period
- May develop at any age
- Autoimmune thyroid disorders occur more frequently in children and adolescents with type 1 diabetes and other autoimmune conditions.
- Chronic lymphocytic thyroiditis prevalence correlates with iodine intake; countries with the highest dietary iodine also have the highest prevalence.
- Subclinical hypothyroidism (TSH concentration between the upper limit of normal reference range and 10 mIU/L, with normal free thyroxine level) found in 7–23% of obese children and 0.3–2% of normal weight controls. It seems to be a consequence rather than cause of the obesity and can normalize with weight loss.
- Family history of thyroid disease or other autoimmune endocrinopathies increases risk.
- Genetic predisposition in patients with chronic lymphocytic thyroiditis; 30–40% of patients have a family history of thyroid disease, and up to 50% of their 1st-degree relatives have thyroid antibodies.
- Weak associations of chronic lymphocytic thyroiditis with certain human leukocyte antigen haplotypes; also associated with genotypes of cytotoxic T lymphocyte–associated 4 (CTLA4) and interleukin-18 (IL-18) genes.
- Autoimmune thyroid disease may be part of type II autoimmune polyglandular syndrome (Schmidt disease).
- Genetic syndromes associated with higher incidence of autoimmune thyroiditis:
- Down syndrome
- Turner syndrome (especially those with isochromosome Xq)
- Myriad causes (see “Differential Diagnosis”)
- Can result from thyroid gland dysfunction (primary hypothyroidism) or from pituitary/hypothalamic dysfunction leading to understimulation of the thyroid gland (secondary and tertiary hypothyroidism)
Commonly Associated Conditions
- Type 1 diabetes
- Other autoimmune conditions
- Pernicious anemia
- Alopecia areata
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