- A) cortisol and cortisone
- B) estrogen and progesterone
- C) thyroxine and triiodothyronine
- D) melatonin and serotonin
Answer:D) melatonin and serotonin
Explanation: Tryptophan is the precursor for neurotransmitter serotonin and melatonin, which is a hormone secreted by the pineal gland. It is an essential amino acid and therefore cannot be produced in the body. It has to be supplemented in the diet.

Also Check:
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- What Controls the Pituitary Gland?
- Is cortisol a stress hormone?
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