Melatonin Is Dose Dependent?

All neurotransmitters, hormones and immune messengers of the Neuro-Endo-Immune Supersytem are Dose-Dependent. Low levels produce one type of effect while high levels creates a different effect. High levels of Melatonin stimulates an inflammatory immune response. While low levels of melatonin promote sleep.

Melatonin is produced in tissues other than the Pineal gland

Melatonin is the major hormone product of the pineal gland. However, this does not make the pineal gland the only place in the body melatonin is produced. But many Professional and Social Media Influencers are unaware of the other organs in the body that produce Melatonin in much greater amounts. 

Melatonin production increases in the pineal gland during the dark phase (night and from Fall Equinox to Winter Solstice). Its secretion from the pineal gland has been classically associated with circadian and circanual rhythm regulation and thus sleep. 

However, melatonin production is not confined exclusively to the pineal gland, but other tissues including retina, tear glands, gut (400X more than Pineal Gland), ovary (200X more than the Gut), testes, bone marrow, thymus and bone marrow of humans and lens also produce it.

The gastrointestinal (GI) tract presents another, many times larger, source of melatonin. Melatonin acts on the immune system by regulating cytokine production of immunocompetent cells. It also possesses the ability to modulate immune responses by regulation of the T helper 1/2/17 balance and cytokine production.

Melatonin production in the gut is 400 x greater than the Pineal Gland.
Melatonin production in the Ovaries is 200 X greater than the Gut, which is 400 X greater than the Pineal Gland. High levels of Melatonin is an important contributor to Polycystic Ovarian Syndrome.
Increased melatonin = increased cell differentiation = Poly (many) Ovarian Cysts
Increased Melatonin levels suppress production of Thyroid Hormones
Immune stimulation from increased levels of melatonin.
Does this sound like a good thing?
Why would they sell them on the internet if they were potentially bad?