Stimulus for prolactin release is -

Ans. is 'd' i.e., Nipple stimulation o Prolactin is structurally similar to GH. Prolactin is physiologically involved in lactation. In a breast which has been primed by female hormones (estrogen and progesterone), prolactin induces and maintains lactation by stimulating synthesis of milk.o Prolactin is the only pituitary hormone which is primarily under inhibitory control of hypothalamus. Its secretion is suppressed by dopamine (Prolactin inhibitory substance) secreted by hypothalamuso Stimulation of numerous mechanoreceptors in the nipple activates a chain of neural afferents leading to the hypothalamus, resulting in the release of prolactin releasing hormone (PRH) which stimulates prolactin secretion. Normally this mechanism plays a subordinate role, but it becomes important when the infant is weanedo The normal prolactin level is < 20 ng/ml. Moderate elevation (30-200 ng/ml) of prolactin can occur in pregnancy, postpartum period, renal failure, liver failure, hypothyroidism, stress, drugs (dopamine antagonists) and prolactinoma. A prolactin level above 150-200 ng/ml is almost always due to a prolactin secreting pituitary adenoma.