Q: Which hormone is classified as a protein hormone?

Insulin is a hormone that is synthesized as a prohormone in the pancreas and is cleaved into its active form, a protein hormone consisting of two polypeptide chains connected by disulfide bonds. Insulin is involved in the regulation of glucose metabolism and helps to lower blood glucose levels by stimulating the uptake of glucose by cells and promoting its storage as glycogen in the liver and muscle tissue.
In contrast, oxytocin and antidiuretic hormone are peptide hormones that are synthesized in the hypothalamus and released from the posterior pituitary gland. Oxytocin is involved in the regulation of uterine contractions during childbirth and milk ejection during breastfeeding, while antidiuretic hormone is involved in the regulation of water balance in the body.
TSH, or thyroid stimulating hormone, is a glycoprotein hormone that consists of a protein subunit and a carbohydrate chain. TSH is synthesized and secreted by the pituitary gland and stimulates the thyroid gland to produce and secrete thyroid hormones, which play a role in regulating metabolism and growth.