Postpartum thyroid dysfunction and the long-term risk of hypothyroidism: results from a 12-year follow-up study of women with and without postpartum thyroid dysfunction.
BACKGROUND
The long-term risk of hypothyroidism following postpartum thyroid dysfunction (PPTD) is uncertain. Most previous studies have been small, short-term or have lacked a control group.


OBJECTIVE
To ascertain the long-term risk of hypothyroidism in women following PPTD. Design and participants A 12-year longitudinal study of 409 women (including 71 with PPTD) who previously participated in a PPTD prevalence study.


METHODS
The primary outcome measure was hypothyroidism (defined as TSH greater than 4 mU/l or on thyroxine replacement) at follow-up. Outcomes in women with and without PPTD were compared by logistic regression. Receiver operating characteristic analysis was used to determine the optimal cut-off for baseline TSH as a predictor of hypothyroidism in the cohort.


RESULTS
At follow-up, hypothyroidism was present in 27 of 71 women who had PPTD at baseline (38%) and 14 of 338 women without PPTD (4%). From multivariate analysis, odds ratios (with 95% confidence intervals) for hypothyroidism were - 4.8 (1.6, 14.1) for PPTD; 8.2 (2.8, 24.6) for positive thyroid peroxidase antibodies (TPOAb); 9.7 (2.6, 37.0) for the hypothyroid phase of PPTD and 51.4 (19.2, 137.5) for hypothyroid PPTD with positive TPOAb. A baseline TSH above 2.6 mU/l was the optimal cut-off for predicting hypothyroidism (sensitivity 76%, specificity 86%).


CONCLUSIONS
PPTD is a strong predictor of hypothyroidism in the long-term. Women who present with postpartum hypothyroidism or have positive TPOAb are at particularly high risk, suggesting that close long-term follow-up is advisable if thyroxine replacement is not instituted at an early stage.
Stuckey
B G A
BG
Keogh Institute for Medical Research, Sir Charles Gairdner Hospital, Nedlands, WA, USA. bstuckey@cyllene.uwa.edu.au
Kent
G N
GN
Ward
L C
LC
Brown
S J
SJ
Walsh
J P
JP
D000328:Adult; D001323:Autoantibodies / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000097:blood* / Q000209:etiology; D007453:Iodide Peroxidase / Q000276:immunology; D016015:Logistic Models; D008137:Longitudinal Studies; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D049590:Postpartum Period; D018570:Risk Assessment; D012307:Risk Factors; D013959:Thyroid Diseases / Q000097:blood* / Q000150:complications; D013972:Thyrotropin / Q000097:blood*; D013997:Time Factors
D001323:Autoantibodies; D013972:Thyrotropin; D007453:Iodide Peroxidase