title: Fecundity in young adults treated early for congenital hypothyroidism is related to the initial severity of the disease: a longitudinal population-based cohort study.
abstract: BACKGROUND
  Untreated hypothyroidism is known to impair fecundity. Patients treated early for congenital hypothyroidism (CH) have yet to be evaluated in adulthood, because screening programs have been running for only the last 30 years in most industrialized countries.
  
  
  OBJECTIVE
  Our objective was to assess the fecundity of young adults treated early for CH and its determinants.
  
  
  METHODS
  Of the 1748 subjects diagnosed with CH in the first 10 yr after the introduction of neonatal screening in France, 1158 completed a questionnaire on fecundity at a mean age of 25.3 yr. This self-administered questionnaire focused on first attempts to have a child and time to pregnancy. The control group was that used in an analogous study on subjects born between 1971 and 1985.
  
  
  METHODS
  Fecundability hazard ratios (HR) were estimated with Cox regression models and adjusted for known fecundity confounders (age, smoking, and reproductive history).
  
  
  RESULTS
  Fecundability was similar for the CH and control groups: HR = 1.14 (0.89-1.47) for women, and HR = 0.98 (0.58-1.66) for men. In women, the most severe initial forms of the disease, athyreosis, absence of bone maturation at the knee epiphyseal ossification centers, and a low serum free T(4) concentration at diagnosis (<5 pmol/liter), were associated with lower fecundity: HR = 0.68 (0.50-0.98) (P = 0.02); HR = 0.65 (0.45-0.94) (p = 0.02) and HR = 0.70 (0.50-0.97) (P = 0.03), respectively. However, fecundability was not associated with age at the start of treatment, initial levothyroxine dose, or the adequacy of hypothyroidism control.
  
  
  CONCLUSIONS
  There is no evidence that fecundity is generally lower in young adults treated early than in the general population. However, fecundity was lower in women suffering from the most severe form of the disease.
authors.affiliation: Pediatric Endocrinology Department, Centre de Référence Maladies Endocriniennes de la Croissance, Institut National de la Santé et de la Recherche Médicale Unité 690, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France.
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Hassani
authors.forename: Béatrice
authors.initials: B
authors.lastname: Larroque
authors.forename: Sophie
authors.initials: S
authors.lastname: Dos Santos
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Ecosse
authors.forename: Jean
authors.initials: J
authors.lastname: Bouyer
authors.forename: Juliane
authors.initials: J
authors.lastname: Léger
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003409:Congenital Hypothyroidism / Q000453:epidemiology* / Q000628:therapy*; D005260:Female; D005298:Fertility; D006801:Humans; D007231:Infant, Newborn; D007247:Infertility, Female / Q000453:epidemiology*; D007248:Infertility, Male / Q000453:epidemiology*; D008137:Longitudinal Studies; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology; D012307:Risk Factors; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult