Part of “CHAPTER 10 – PINEAL GLAND“

Plasma levels of melatonin seem to reflect closely the amount being synthesized and secreted by the pineal gland (see Fig. 10-3).6 When pineal melatonin production increases at night, plasma levels rise accordingly. In the few individuals in whom the pineal has been surgically removed because of tumors in the epithalamic region, plasma levels of melatonin either are severely depressed or are undetectable.7 In animals, pinealectomy is associated with very low or nonmeasurable amounts of melatonin in plasma.