Objective: The long-term effect of the subclinical form of postpartum thyroid dysfunction (PPTD) has not been well established. This study was conducted to evaluate the outcome of permanent hypothyroidism in a large cohort of women with PPTD.
Design and methods: Of 213 women with PPTD, 172 (81%) returned for follow-up. There were 27 (16%) with subclinical (group 1) and 145 (84%) with overt hypothyroidism (group 2). They were all treated with levothyroxine for 23 +/- 16 months and followed-up for thyroid function after thyroxine (T(4)) withdrawal.
Results: In group 1, the time of occurrence of PPTD was longer, serum T(4) was higher and TSH was lower than in group 2. After T(4) withdrawal, 59 and 64% of patients became hypothyroid in groups 1 and 2 respectively; however, serum TSH was increased in group 2 as compared with group 1 (29.7 +/- 8.4 vs 16.4 +/- 15.4 mU/l, P < 0.002). The duration of euthyroidism, serum free T(4) and triiodothyronine indices and thyroperoxidase antibodies were not significantly different between the two groups.
Conclusion: It was concluded that a high percentage of patients with the subclinical form of PPTD proceed to permanent thyroid failure. The timely recognition of mild to severe cases of PPTD is important for the improvement of life for mothers and infants.