Replacement therapy is the administration of exogenous supplemental hormones to compensate for the body’s original endocrine glands due to a lack of a certain hormone, and the hyposecretory function due to pathological changes, surgery or physical degeneration, and this therapy is called replacement therapy. Clinically common ones are, for example, hypothyroidism, which is due to a lack of thyroid hormones and can be supplemented with oral artificial thyroid hormones. Diabetes mellitus is caused by insufficient insulin deficiency and can be treated by applying synthetic insulin instead. There is also renal failure and uremia, which requires the application of dialysis machines to replace the kidneys to complete the metabolism. There is also menopause in women who are menopausal and have hormonal problems that can be treated with oral estrogen supplementation.