Buy AumSum Merchandise: Website: In need of energy, the pituitary gland present in our brain releases Thyroid Stimulating Hormone. This hormone informs the thyroid gland present in our neck to release hormones like thyroxine and triiodothyronine which instruct our cells to burn calories and in turn produce energy. This is basically called metabolism. However, in some conditions like hyperthyroidism and hypothyroidism, our thyroid gland doesn’t respond properly to the pituitary gland. In hyperthyroidism, it releases more hormones even when we don’t require extra energy. This increases metabolism, causing our cells to burn more calories, and thus leading to weight loss. While in hypothyroidism, it releases very less hormones, causing our cells to burn fewer calories, thus leading to weight gain.