Has she breastfed for at least 6 months? Has she suffered from postpartum depression ? Is there any other major change in lifestyle after delivery? Pinpointing the reason with a corrective measure can aid in weight loss .Eating lesser calories in a day without leaving out on all healthy food groups with a minimum of 150minutes exercise per week, will ensure weight loss regardless of thyroid malfunction. Ideal body weight-55kgs for your height.