Which organ is part of both the endocrine and the reproductive systems?

The testes are crucial components of both the endocrine and reproductive systems. They produce sperm, which is essential for reproduction, while also secreting hormones such as testosterone. Testosterone plays a vital role in the development of male reproductive tissues, secondary sexual characteristics, and overall regulation of various bodily functions, thereby linking the endocrine system with reproductive processes.

In contrast, the pancreas primarily functions within the digestive system by producing enzymes to aid in food digestion but also has an endocrine role by secreting insulin and glucagon. The thyroid is primarily involved in regulating metabolism through hormone production but does not directly participate in reproductive functions. The spleen is part of the lymphatic system and supports immune functions, without involvement in either the endocrine or reproductive systems.