In the context of primary lymphoid organs, the thymus gland secretes which hormone involved in T-lymphocyte maturation?

• A. Thymosin
• B. Cortisol
• C. Melatonin
• D. Erythropoietin (EPO)

Answer: (A)

Verified step by step guidance

1. Understand the role of primary lymphoid organs: These organs are responsible for the production and maturation of lymphocytes, which are critical cells in the immune system.
2. Identify the thymus gland as a primary lymphoid organ where T-lymphocytes mature. The thymus provides an environment for immature T-cells to develop and become functional.
3. Recognize that the thymus gland secretes a specific hormone that promotes the maturation and differentiation of T-lymphocytes. This hormone is essential for the proper development of the immune response.
4. Recall the names and functions of the hormones listed: Cortisol is a stress hormone, Melatonin regulates sleep cycles, and Erythropoietin (EPO) stimulates red blood cell production, none of which are involved in T-cell maturation.
5. Conclude that the hormone secreted by the thymus gland involved in T-lymphocyte maturation is Thymosin.