The pineal gland produces the hormone melatonin from the amino acid tryptophan, the website Mayo Clinic states. The synthesis and release of melatonin from the brain is triggered by darkness and suppressed by the light. Melatonin may play a role in your body's circadian rhythm, which regulates sleep patterns.
Melatonin also has antioxidant properties, which may explain why there is some evidence it could help regrow, or perhaps just slow, hair loss when used topically on the scalp.
Strong scientific evidence shows that melatonin helps people recover more quickly from jet lag, relieves insomnia in the elderly, and alleviates a condition called delayed sleep phase syndrome in people of all ages.
There are three phases of hair growth. The growth stage is called the anagen phase, and it can last from two to five years. A transitional phase, called the catagen phase, lasts for a few days. Hair is shed in the telogen phase, and then the cycle starts all over again when your hair follicles sprout new hairs. If the follicles don't spout new hairs, thinning and baldness follow. Some theorize that melatonin, with its antioxidant properties, can fight free radicals and heal damage to hair follicles.
The study cited most frequently in support of melatonin as a hair growth supplement was conducted in 2004 at Friedrich-Schiller University in Jena, Germany. The research subjects who rubbed melatonin into their scalps during the trial period increased the rate of hair growth during the anagen phase when compared to a group who used placebos. In their finding, the researchers stated "This pilot study is the first to show that topically applied melatonin might influence hair growth."
While it appears to be safe to use topical hair growth products with melatonin, taking melatonin supplements orally can produce side effects. As Brent Bauer, clinical internist at the Mayo Clinic writes, melatonin supplements can cause dizziness, headaches, stomach discomfort, confusion, nightmares and sleep walking. Melatonin can interact with blood-thinners, immunosuppressants and medications for diabetes and birth control.
While there is some research to support the notion that melatonin can help regrow hair, or at least slow hair loss, the jury is still out. At the present time, as the Mayo Clinic states, over-the-counter remedies for hair loss have no proven benefits.