A. Parathyroid hormone (PTH) increases the Ca2+ levels in the blood . B. Epinephrine and Nor-epinephrine are called emergency hormones or hormones of Fight or Flight as they are secreted in response to stress . C. Thyroid stimulating hormone (TSH) stimulates the synthesis and secretion of thyroid hormones from the thyroid gland . D. Melatonin plays a very important role in the regulation of the 24-hour (diurnal) rhythm of the body, essentially regulating the biological clock .