Hi, Thanks for the query. I understand your concern. Duoluton -l is a combined hormone contraceptive. while it is given with Eltroxin, the estrogen part of Duoluton makes some of Eltroxin inactive, thus increase in need of Eltroxin Or agrravating effects of hypothyroidism. Hypothyroidism is known to cause menstrual irregularities. That is why in spite of correction, the hypothyroidism remains uncompensated for & cause irregular periods , when give with contraceptive like Duoluton l. In such a case you need to - * - Consult your gynecologist to change the hormone for menstrual regulation ( having progesterone only ) OR.. - Increase the dose of thyroid supplement. * & check for regular menses & thyroid hormone normality in blood... Thanks.