Cortisol or hydrocortisone is the principal glucocorticoid hormone (corticosterone is more abundant in some small mammals). It regulates the glucose metabolism and promotes gluconeogenesis, especially during starvation and raises blood pressure. Cortisone is an inactive form of cortisol.

Thyroxine, the principal hormone, of thyroid gland, is required for tissue differentiation and metamorphosis (the rapid transformation from the larval to the adult form) in amphibians. Thyroxine triggers a response from the hypothalamus, (probably by a genetic mechanism) followed by the production and release of TSH (Thyroid stimulating hormone), thus metamorphosis begins and tadpoles metamorphose into frogs. Thiourea is an organic compound of carbon, nitrogen, sulphur and hydrogen, with the formula CSN₂H₄, or (NH₂)₂CS. It is similar to urea, except that oxygen atom is replaced by a sulphur atom.

Deoxyribonuclease and ribonuclease are secreted by pancreas. These enzymes act on DNA and RNA and convert them to deoxyribonucleotides and ribonucleotides, respectively. The optimum pH required by pancreatic juice to secrete these enzymes is 7-8 (alkaline).

Atrial natriuretic factor (ANF) is released by wails of the cardiac atrium in response to high sodium concentration, high extracellular fluid volume, or high blood volume. It then acts via various mechanisms to excrete Na, and to cause vasodilation in the circulatory system. It also decreases Na resorption in the renal distal convoluted tubule and cortical collecting duct. It also inhibits renin secretion.

Gastrin is a polypeptide hormone produced by the enteroendocrinc cells of the stomach. It plays an important role in the control of gastric acid secretion.

Inhibin hormone is secreted from corpus luteum, placenta and testes. It supplements the effect of excess sex hormones for depressing gonadotrophic activity (FSH, LH, ICSH) target of inhibin is anterior lobe of pituitary.

Duodenal enterokinase converts trypsinogcn to activate trypsin which, in turn, activates the other pancreatic enzymes.

The thymus gland is located behind the sternum and between lungs. It is only active until puberty. After puberty, the thymus starts to shrink slowly and become replaced by fat.

The thyroid gland is a vital hormone gland. It plays an important role in the metabolism growth and development of the human body. It helps to regulate many body functions by constantly releasing a steady amount of thyroid hormones into the bloodstream. Cretinism is a type of mental retardation and bodily malformation caused by severe, uncorrected thyroid deficiency.

The major function of parathyroid gland is to maintain the body's calcium and phosphate levels within a very narrow range, so that the nervous and muscular systems can function properly. It secretes parathyroid hormone. It also enhances the excretion of phosphate by the kidneys and its uptake by the cells.

Pancreas is an organ present in abdomen. It plays an essential role in converting the food we eat into fuel for the body's cells. Delta cells is a type of cell found in Islets of Langerhans in pancreas. They form somatostatin, a hormone that inhibits the release of numerous hormones in the body.

Gastrin stimulates the gastric secretion. It is released from the gastric glands.

Enterogasterone is secreted by the duodenal epithelium. It inhibits the secretion of gastric juice and slows gastric contraction.

CCZ- PZ or Cholecystokinin pancreozymin is secreted by entire small intestine. It stimulates the gall bladder to release bile and the pancreas as to release enzymes in the pancreatic juice.

Villikinin accilerates the movement of intestinal villi.

Almost all secretion by the pituitary gland are controlled by hormonal signal from hypothalamus. The neurohormones are secreted and accumulated by hypothalamus.

Adrenaline (epinephrine) is a hormone produced by adrenal medulla and is secreted in great amounts during emotional states. It elevates the glucose level in blood stream (by glucogenesis) which is accompanied by an increase in oxygen consumption, body temperature, heat production. Adrenaline also causes an increase in the flow of blood by dilating the blood vessels.
Insulin regulates the glucose level in blood.
ACTH (Adreno Corticotropic Hormone) is secreted by the anterior pituitary and stimulates the adrenal cortex.
Glucagon is a polypeptide hormone secreted by the alpha cells of islets of langerhans of pancreas. It acts to promote glycogenolysis.

Gonadotropins or gonadotropic hormones are as follows.

(a) Follicle Stimulating Hormone (FSH) : It stimulates growth of ovarian follicles and their secretion of oestrogen in the female and spermatogenesis in the male.

(b) Interstitial Cell Stimulating Hormone (ICSH) : It activates the Leydig's cells of the testis to secrete androgens. In female it stimulates the corpus luteum of the ovary to secrete progesterone. In female ICSH is termed as LH (Luteinizing Hormone).

Second messengers are the organic molecules and sometimes the metal ions, acting as intracellular signals, whose production or release usually amplifies a signal such as a hormone, received at the cell surface.
Sodium (Na) is not a second messenger to be discovered.
In addition to cyclic AMP, Cyclic Guanosine Monophosphate (CGMP) functions as a second messenger in certain cases.
Calcium ions (Ca⁺⁺) also act as second messenger in phospholipase  second messenger system.