During the birth process, the pituitary hormone __________ signals the uterus to contract.

Pituitary gland:

1. The pituitary gland is also known as the master gland because it controls all the other endocrine glands to secrete their hormones.
2. For example, Thyroid-stimulating hormone (TSH), released by the pituitary gland stimulates the thyroid gland to secrete thyroxine.
3. The posterior lobe of the pituitary gland secretes oxytocin, which stimulates milk production from mammary glands and produces uterine contractions during childbirth.

Final answer: During the birth process, the pituitary hormone oxytocin signals the uterus to contract.