Hello Lisagarmaise, Serotonin is to blame! Excessive release of 5HT(serotonin) from intestinal mucosa cells can cause diarrhea and nausea. Metformin stimulates these intestinal cells to produce increased levels of 5HT, as soon as 10-15 minutes after taking metformin. The good news is that most symptoms dissapear after taking metformin for 2-3 weeks.
Progesterone, hormone secreted by the female reproductive system that functions mainly to regulate the condition of the inner lining (endometrium) of the uterus. Progesterone is produced by the ovaries, placenta, and adrenal glands.
Hormones are produced by endocrine glands. In humans and many other animals, hormones are either peptide hormones (modified amino acids, peptides, small proteins) or steroid and steroid-like hormones. The endocrine glands are ductless glands and secrete hormones directly into the blood vessels nearby. The hormones are then carried throughout the body and act upon target cells and tissues. The target cells have protein receptors which recognize the hormone and bind it. This interaction of the hormone and its specific receptor occurs either in the cell membrane (amino acid, peptide, or small protein hormone) or in the cell interior (steroid hormones).