the first thing that people need to know is that calorie restriction reduces thyroid function so if you are going on any sort of calorie restrictive nutrition diet you will see a decrease in thyroid function so think of it this way your thyroid gland is related to your fertility as a woman and if your body senses that there is less nutrients and calories nutrition available to it it will try to conserve what it has so it will reduce the metabolic rate in order to conserve