The organ that was considered vestigial until recently but is now confirmed to be an endocrine gland is the "pineal gland."

The Pineal Gland:
The pineal gland is a small, pinecone-shaped gland located in the brain. It was long considered vestigial, meaning it had no significant function and was simply a remnant of our evolutionary past. However, recent research has revealed that the pineal gland is indeed an endocrine gland, producing important hormones that regulate various bodily functions.

Melatonin Production:
The primary hormone produced by the pineal gland is melatonin. Melatonin helps regulate the sleep-wake cycle, also known as the circadian rhythm. It is responsible for signaling the brain when it is time to sleep and when to wake up. The production of melatonin is influenced by environmental factors such as light and darkness.

Regulation of Hormones:
The pineal gland also plays a role in regulating other hormones in the body. It interacts with the hypothalamus, a region of the brain that controls the release of hormones from the pituitary gland. The pineal gland helps regulate the secretion of hormones such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are involved in reproductive functions.

The Third Eye:
The pineal gland has also been referred to as the "third eye" due to its unique anatomical and functional characteristics. It contains light-sensitive cells that can detect changes in light levels. This light detection ability is thought to play a role in the regulation of the circadian rhythm and the production of melatonin.

Research and Confirmation:
Advancements in medical imaging techniques and molecular biology have allowed scientists to study the pineal gland in more detail. They have discovered the presence of specific receptors for melatonin and identified the genes responsible for its synthesis. These findings have confirmed the pineal gland's role as an endocrine gland.

In conclusion, the organ that was once considered vestigial but is now known to be an endocrine gland is the pineal gland. It produces the hormone melatonin, which regulates the sleep-wake cycle and interacts with other hormonal systems in the body. The pineal gland's unique anatomical features and light sensitivity have led to its association with the concept of the "third eye." Recent research has provided confirmation of its endocrine function, overturning the previous notion of it being a non-functional vestige.

Pineal gland was considered to be vestigial till 1950.Later the discovery of melatonin secreted by pineal it was concluded as endocrine gland