Which hormone is produced by the posterior pituitary that regulates water balance, and is secreted in larger amounts during pregnancy?

Which hormone is produced by the posterior pituitary that regulates water balance, and is secreted in larger amounts during pregnancy?

• A. Oxytocin and AVP
• B. Melatonin and dopamine
• C. Growth hormone and prolactin
• D. TSH and ACTH

Answer: (A)

The key concept is that the posterior pituitary releases two important neuropeptides: vasopressin (antidiuretic hormone) and oxytocin. Vasopressin is the one that regulates water balance by acting on the kidneys to promote water reabsorption, reducing urine output. During pregnancy, oxytocin is released in larger amounts to support labor and lactation. So a choice that includes both hormones from the posterior pituitary—and notes that oxytocin increases during pregnancy—best matches the physiology. Other options mix hormones that are not produced by the posterior pituitary or are not primarily involved in water balance, such as melatonin and dopamine (pineal and hypothalamic/neurotransmitter roles), and growth hormone with prolactin or TSH and ACTH (produced by the anterior pituitary).

The key concept is that the posterior pituitary releases two important neuropeptides: vasopressin (antidiuretic hormone) and oxytocin. Vasopressin is the one that regulates water balance by acting on the kidneys to promote water reabsorption, reducing urine output. During pregnancy, oxytocin is released in larger amounts to support labor and lactation. So a choice that includes both hormones from the posterior pituitary—and notes that oxytocin increases during pregnancy—best matches the physiology.

Other options mix hormones that are not produced by the posterior pituitary or are not primarily involved in water balance, such as melatonin and dopamine (pineal and hypothalamic/neurotransmitter roles), and growth hormone with prolactin or TSH and ACTH (produced by the anterior pituitary).