TSH variations on/off LT4 therapy in hypo-HT women diagnosed with PPT. A significant reduction in TSH levels was observed between T1 and T2 (1.06 ± 0.72 mU/L vs 0.07 ± 0.10, P-value = 0.00042), despite similar LT4 dosages at these points in time (1.51 ± 0.39 mcg/kg/die vs 1.57 ± 0.44, P-value = 0.062). At T3, all the women had discontinued LT4 therapy, and their TSH values markedly increased up to 33.2 ± 56.6 (range 0.03-234.9 mU/L) to spontaneously decrease to 9.73 ± 12.07 mU/L at T4. Following this point, LT4 therapy was restored in all hypo-HT women, with the exception of 1 woman who showed a later PPT onset (TSH suppression up to 24 weeks postpartum followed by the previously described pattern of TSH changes between 28 and 33 weeks after delivery). The 5 time points after delivery (T1 through T5) are as follows: T1 = 6.7 ± 0.9 weeks; T2 = 13.6 ± 1.2 weeks; T3 = 19.1 ± 1.3 weeks; T4 = 23.6 ± 1.6 weeks; and T5 = 51.3 ± 1.4 weeks.