Position. The epiphysis is an odd gland located in the center of the brain, at the level of the diencephalon, and more precisely above and behind the third ventricle, a cavity containing cerebrospinal fluid (1) (2).

Structure. Conical in shape and measuring 6 to 10 mm long, the epiphysis is made up of secreting cells called pinealocytes. The latter group together in clusters and compact cords within the epiphysis. These cells are particularly responsible for the secretion of melatonin, considered to be “the sleep hormone” (2). The epiphysis is also found in relation to the suprachiasmatic nucleus of the hypothalamus, involved in the biological clock (1) (2).

Internal clock operation. The epiphysis has an endocrine function with the secretion of melatonin. This hormone has a circadian effect, i.e. impacting on the internal clock which corresponds to the functioning of the body according to the time of day (1). The regulation of the internal clock follows a precise process under the control of the epiphysis. First, the epiphysis receives visual information including the intensity and duration of light during the day. This information travels through the retina, the suprachiasmatic nucleus of the hypothalamus, the superior cervical ganglion before reaching the epiphysis. Depending on the information received, the epiphysis secretes melatonin, a hormone that induces drowsiness. This secretion reaches its maximum in the middle of the night and its minimum in the middle of the day (1).

Other Functions. The endocrine function of the epiphysis may have effects on the development of the sexual tract. Recent studies also show that it could intervene in the regulation of the production of detoxifying and antioxidant molecules within the body (1).

Head trauma. It corresponds to a shock to the skull which can cause brain damage. (3)

Brain tumors. Benign or malignant tumors can develop in the pineal region. (4)

Rett Syndrome. This rare genetic disease causes abnormal development of the central nervous system, and manifests itself in children from 6 to 18 months old. This syndrome is characterized by intellectual disability and can lead to various disorders: respiratory, cardiac, motor, sleep, etc. (5)

Sleeping troubles. Dysfunction of the epiphysis can lead to sleep disturbances such as insomnia.

Seasonal depression. Linked to a decrease in the supply of natural light, this condition is a recurring disorder appearing every year in autumn and winter. Involved in the cycle of the internal clock, the epiphysis can impact on this seasonal depression.

Drug treatments. Depending on the pathology diagnosed, certain treatments may be prescribed such as painkillers.

Surgical treatment. Depending on the type of pathology diagnosed, surgery may be performed.

Chemotherapy, radiotherapy, targeted therapy. Depending on the type and stage of the tumor, these treatments may be implemented.

Genetical therapy. Research is underway to develop this type of therapy in the context of genetic diseases such as Rett Syndrome. (5)

Light therapy. This practice consists of providing artificial white light to temporarily replace the sun’s rays.

Physical examination. First, a clinical examination is performed in order to identify and assess the symptoms perceived by the patient.

Medical imaging exam. In order to assess damage to the epiphysis, a brain scan or a brain MRI can in particular be performed.

biopsy. This examination consists of a sample of cells, making it possible in particular to analyze the tumor cells.

The epiphysis is an ideal point of reference for certain medical imaging examinations. In adulthood, concretions of calcium salts are created between the pinealocytes, forming the pineal sand. The latter is opaque and makes it possible to create a black mark during x-rays (2).