In normal circumstances, however, the SCN reacts to the lengthening nights by instructing the brain's pineal gland to secrete more of the hormone called melatonin.

然而，在正常情况下，SCN对夜晚延长的反应是，它会指示大脑的松果腺增加褪黑激素的分泌。

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This mechanism is associated with melatonin, a pigment secreted by the pineal gland, though scientists are not sure exactly how it operates.

该机制与松果腺分泌的一种色素---褪黑素有关，虽然科学家还不确定其如何起作用。

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Melatonin, a hormone produced by the pineal gland in response to darkness, is thought to play a primary role in controlling the body's circadian rhythm.

褪黑激素，黑暗时松果腺产生的一种激素，被认为在控制身体昼夜节律起主要作用。

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The reason for this conflicting opinion is that as well as being available in pill form, melatonin is also produced naturally by the pineal gland of the brain and is present in certain foods.

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Melatonin products are usually synthetic versions of the hormone made naturally by the pineal gland, in the brain, which helps regulate the body's sleep-wake cycle.

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