Suckling in lactating women stimulates the secretion of insulin and prolactin without concomitant effects on gastrin, growth hormone, calcitonin, vasopressin or catecholamines.

The levels of growth hormone, vasopressin, prolactin, calcitonin, gastrin, insulin, epinephrine, norepinephrine and dopamine were measured in six lactating women during breast feeding. Prolactin levels increased in response to suckling as expected. In addition, insulin levels rose two-fold. No consistent changes were observed in the levels of the other hormones. It is suggested that the suckling related insulin release is either secondary to a reflexly induced activation of the vagal nerves or to the increased circulating levels of prolactin. Furthermore, it is suggested that the insulin release in response to suckling participates in the stimulation of milk production.