Hypothyroidism is characterize by the low activitiy of your thyroid gland to process the hormone released by the pituitary gland. This hormone is called TSH or the Thyroid stimulating Hormone. Once your thyroid detects that the pituitary gland sends TSH, it releases also two hormones (T3 and T4) in order to control the metabolism of your body. There are 4 types of hypothyroidism but three of which are common, Primary, secondary and Tertiary. The answer to the question asked above is the Secondary Hypothyroidism. Secondary Hypothyroidism is due to the inactivity of the pituitary gland thereby reducing the level of TSH.