Hormonal Control of Lactation

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To start and keep a milk supply, prolactin and oxytocin are required. A hormone called prolactin stimulates the production of milk. Suckling is a significant stimulator of prolactin release, increasing prolactin levels by twofold.

Prolactin levels are also elevated at times of stress, sleep, and sexual activity. Prolactin activity is suppressed during the final three months of pregnancy to allow the mother's body to prepare for milk production without making milk & this happen  because of the prolactin-inhibiting factor that the hypothalamus secretes. Prolactin is required for milk synthesis but its actual blood level does not correlate with how much milk is produced.

Hormones that support breastfeeding and breast development

Hormone

Role in lactation

Stage of lactation

Estrogen

Ductal growth

Mammary gland differentiation with menstruation

progesterone

Alveolar development

After onset of menses and during pregnancy

Human growth hormone

Development of terminal end buds

Mammary gland development

Human placental lactogen

Alveolar development

Pregnancy

prolactin

Alveolar development & milk secretion

Pregnancy & breast feeding (from the third trimester of pregnancy to weaning.)

oxytocin

Let-down: ejection of milk from myoepithelial cells

From the onset of milk secretion to weaning

Sucking or nipple stimulation can also trigger the release of oxytocin. Letdown, or the ejection of milk into the milk ducts from the milk gland (acinus), is its primary function. When the milk ducts compress, women may feel tingling or occasionally intense shooting pain that lasts for about a minute. During and after delivery, oxytocin also affects the uterus, causing it to constrict, seal blood vessels, and reduce in size.

References:
Brown, J. E., 2017. Nutrition through the lifecycle. In: J. E. Brown, ed. Nutrition Through the Life Cycle. USA: s.n., pp. 182 -183.

 

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