A glandular secretion was any chemical produced by a gland, such as venom. (TNG: "Genesis")
A glandular secretion was developed by the bodies of the female members of Theela's species in response to the energy-draining properties of their new homeworld in the Taurean system. Though it aided their survival by warding off the effects of aging and death, it also allowed them to manipulate the emotions of the males of that species, eventually weakening all the males to the point of death. In 2269, several male crewmembers of the USS Enterprise came under the influence of this secretion. (TAS: "The Lorelei Signal")
Potak cold fowl was made from the glandular secretions of an adult dunghill bird. (VOY: "Parturition")