reproductive system excretory system endocrine system circulatory system
I gave my students this multiple choice question: What organ system in the human body contains the pituitary gland, hypothalamus gland, and thyroid gland?

Only one answer is correct among these 4 choices:
- reproductive system
- excretory system
- endocrine system
- circulatory system

Could you tell me which one is correct?

endocrine system