Hormones are produces in a number of different tissues, and to know where it is formed you should try narrowing your search by the specific hormone in question before looking at which tissue produces it. Hormones are generally formed by endocrine organs, but may also be produced by the heart (ANP) or skin (Vitamin D) as well as other places. Endocrine organs include the pituitary, pineal, thyroid, parathyroid, adrenal glands, pancreas (exocrine and endocrine) and others. Hormones can also be produced by the placenta during pregnancy.