Pregnenolone is a hormone with its own actions, as well as being a mother hormone for sex and adrenal hormones. It is available over the counter although caution is advised with regard to hormone use. This hormone's level can be determined in the laboratory but it is an uncommon test. Many holistic doctors will test for it and other hormones with a urine sample. Estrogen-deficient women often are low in pregnenolone, an essential hormone (derived from cholesterol) which is a precursor to progesterone. Pregnenolone may be a significant contributing factor in depression. Pregnenolone is abundant in the brain where it improves the transmission of nerve impulses and facilitates communication between brain cells. In a sense, people who are depressed may have poor communication, neuronally speaking, between the different parts of their brain because they are deficient in pregnenolone. This hormone appears to have a great calming effect because it activates receptor sites in brain cells for GABA (itself a calming agent), enabling more GABA to be absorbed by the cells.