Thymus gland

Thymus gland is large and active gland in the newborn, reaches full activity at puberty and thereafter declines in activity slowly. The thymus is a lymphoid organ found on both sides of the trachea.

During its early development, it resembles an endocrine gland and is essential for the normal development and maintenance of immunologic competence.

Thymic hormones are the homeostatic thymic hormone (HTH), thymic humoral factor (THF), thymosin, and lymphocyte-stimulating hormone (LSH).

HTH and LSH increase the ratio of lymphocytes to polymorphonuclear leukocytes(PMN). Thymosin and THF stimulate cell-mediated immunity. A thymic steroid substance thymosterin inhibits lymphocytopoiesis and tumor growth