Paper
Updating the Pineal Gland Mystery: Purpose and Function in Children and Adult Health and Pathology
Published 2021 · Nicholas A. Kerna, N. V. Carsrud, Uzoamaka Nwokorie
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Abstract
The human pineal gland is considered as a “type A” organ, meaning it lies proximal to the third ventricle. It is principally comprised of two cell types: pinealocytes, which make up most of the gland (85–90%), and glial cells (mostly astrocytes). The gland is relatively small in < 2-year-old children. Moreover, its size does not significantly change between 2–20 years of age. The pineal gland is a neuroendocrine organ that secretes the hormone melatonin. The pineal body is thusly implicated in pigmentation, reproductive organ functions, seasonal breeding, and jet lag. It is also referred to as a “biological clock” [10] that plays a crucial role in regulating the circadian rhythm in humans. The pineal gland also produces N, N-dimethyl-tryptamine (DMT), that is found in certain plants and acts as a hallucinogen. The pineal gland is aptly called a neuroendocrine transducer as it converts the neuronal signals into hormones, affecting various physiological functions and conditions of an organism. Calcification (calcium deposits) is a landmark feature of the pineal gland on x-ray and magnetic resonance imaging (MRI). The degree of calcification depends on age and is usually very high in individuals older than 30 years. Calcification is typically caused by the deposition of hydroxyapatite, leading to reduced melatonin secretion. Pineal calcification has been implicated in Alzheimer’s disease. Pinealectomy is the surgical removal of the pineal gland for medical reasons. However, only a few studies have investigated the effect of pinealectomy on humans. Studies on the pineal gland have been aimed at determining its effects on human physiological processes and those of other organisms. The presence of melatonin from the protozoa to highly evolved mammals indicates the gland’s significance. Thus, it is imperative to gain further insights into and understanding of this gland and its hormones to uncover more practical therapeutic and preventive options. Dysregulation of melatonin secretion can occur in several pathophysiological conditions. In scoliosis, the spine curves abnormally toward one side. Currently, there is insufficient evidence to confirm the relationship of melatonin in adolescent idiopathic scoliosis, although it is being considered. In humans, melatonin facilitates osteoblast (cell) differentiation. Pineal gland tumors have been rarely reported. However, pineoblastoma and pineocytoma have been observed in adults. Pineal-origin breast cancer seldom occurs unless a pineal tumor metastasizes to distinct tissues and organs, such as breast tissue. For this reason, the pineal gland is sometimes referred to as the oncostatic structure in the brain. Children with autism spectrum disorder (ASD) commonly experience insomnia and display behavioral problems. Notably, clinical studies have suggested a direct association between ASD and diminished melatonin levels. This review investigates and summarizes pineal gland purpose and function in humans, and hopefully helps decipher the great “mystery” surrounding this relatively small but significant gland.
The pineal gland plays a crucial role in regulating human physiological functions and circadian rhythm, with potential implications for Alzheimer's disease and scoliosis.
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