What occurs when the feedback inhibitor of lactation (FIL) builds up?

When feedback inhibitor of lactation (FIL) accumulates in the mammary glands, it signals to the body that there is adequate milk present and reduces the production of new milk. FIL is a protein produced in the breast milk that inhibits further milk synthesis when it reaches a certain concentration. As the levels of FIL rise, the feedback mechanism effectively communicates to the breast tissue that less milk is needed, leading to a decrease in milk production. This helps regulate milk supply to match the infant's needs and prevent overproduction.

The increase in prolactin levels, an important hormone for milk production, does not happen in response to rising FIL levels, as FIL's role is to suppress lactation activity when enough milk is present. Likewise, the characteristics of milk, such as becoming more watery, aren't directly affected by FIL. Oxytocin, which is involved in milk ejection during nursing, is not released as a direct result of FIL accumulation either; instead, it's linked to the stimulation of breastfeeding.