The figure shows six endocrine glands of the human body, numbered 1 to 6. Which numbered gland makes melatonin, the hormone of the 24 hour rhythm?

Fig. 1: The outline of the human body with six numbered glands. The head shows gland 1 at the base of the brain and gland 2 above it. The neck shows gland 3 in front of the windpipe. Gland 4 lies behind the breast bone. Gland 5 sits on top of the kidney. Gland 6 lies behind the stomach.