What is a 'Z-Score'. A Z-score is a numerical measurement of a value's relationship to the mean in a group of values. If a Z-score is 0, it represents the score is identical to the mean score. Z-scores may also be positive or negative, with a positive value indicating the score is above the mean and a negative score indicating it is below the mean.
The pineal gland, also known as the pineal body, is an important endocrine gland that produces the hormone melatonin. Melatonin plays a key role in the sleep/wake cycle and the bodyâs response to sunlight. The pineal gland is a small, pinecone-shaped mass of glandular tissue about 1/3 of an inch (8 mm) long.
Melotonin is the only hormone secreted by the pineal gland. (The pineal gland is a tiny endocrine gland situated at the centre of the brain.) Melatonin was discovered in 1958 by Aaron B. Lerner and other researchers working at Yale University. Melatonin is produced in humans, other mammals, birds, reptiles, and amphibians. It is present in very small amounts in the human body.