The starting point for this adventure is the well-established observation that Calcium requirements for breastfeeding generate a loss of bone formation, estimated at 10% in women and 30% in female rodents. Normally, nature is well done, estrogens compensate for this by slowing down bone resorption – remember that 3 types of bone cells contribute to the genesis and resorption of bones which are in constant regeneration. However, levels of this hormone drop during lactation. Suddenly, the question arose of the possible compensatory mechanism which would prevent too sudden a drop in bone formation during breastfeeding. The authors show that during breastfeeding, the blood contains a molecule that promotes the formation of bone mass. Additionally, during lactation, there is a burst of release of this molecule in the region of the brain that produces it – the Arcuate Nucleus. This new hormone – called CCN3 – stimulates the cellular activity of the skeleton, increases bone formation in women and rodents, and accelerates the repair of bone fractures in both sexes. Nice work that goes off the beaten track, asking a major question and finding the means to answer it. Breastfeeding like parturition are moments involving biological mechanisms of enormous complexity developed over centuries to guarantee the survival of the species.
