The increased incidence of congenital hypothyroidism: fact or fancy?

UMMS Affiliation

Department of Pediatrics

Publication Date


Document Type



Child; Cohort Studies; Congenital Hypothyroidism; Female; Follow-Up Studies; Humans; Incidence; Infant; Infant, Newborn; Male; Massachusetts; Neonatal Screening; Severity of Illness Index; Up-Regulation


Cell Biology | Congenital, Hereditary, and Neonatal Diseases and Abnormalities | Developmental Biology | Endocrine System Diseases | Endocrinology | Musculoskeletal Diseases | Pediatrics


OBJECTIVE: The incidence of congenital hypothyroidism (CH) detected by newborn screening in the US has increased significantly since the early 1990s. We defined the characteristics associated with the increased incidence.

PATIENTS: A cohort of children with CH born during an earlier period of low incidence (1991-94) was compared with a cohort born during a later period when the incidence of CH had doubled (2001-04).

MEASUREMENTS: Screening was performed with T4 as the primary marker and thyroid stimulating hormone (TSH) on selected specimens. Follow-up on hypothyroid children determined whether they had permanent or transient hypothyroidism. Cases were classified based on laboratory results: initial TSH >/=100 mU/l was 'severe,' initial TSH /l but >/=20 mU/l was 'mild' and initial TSH /l with subsequent abnormal TSH was 'delayed'.

RESULTS: The overall incidence of CH almost doubled between the two time periods, from 1:3010 to 1:1660. Excess cases were found in the mild and delayed categories, with no increase in severe cases. The proportion of transient cases was

CONCLUSION: The rising incidence of CH in Massachusetts is confined to mild and delayed cases. Our findings suggest that this rise is attributable to enhanced detection rather than an absolute increase in numbers.

DOI of Published Version



Clin Endocrinol (Oxf). 2011 Dec;75(6):806-10. doi: 10.1111/j.1365-2265.2011.04128.x. Link to article on publisher's site

Journal/Book/Conference Title

Clinical endocrinology

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PubMed ID