Unsolved Mysteries of the Human Mammary Gland: Defining and Redefining the Critical Questions from the Lactation Consultant's Perspective.

Despite advances in knowledge about human lactation, clinicians face many problems when advising mothers who are experiencing breastfeeding difficulties that do not respond to normal management strategies. Primary insufficient milk production is now being acknowledged, but incidence rates have not been well studied. Many women have known histories of infertility, polycystic ovary syndrome, obesity, hypertension, insulin resistance, thyroid dysfunction, hyperandrogenism or other hormonal imbalances, while others have no obvious risk factors. Some present with obviously abnormal breasts that are pubescent, tuberous/tubular or asymmetric in shape, raising the question of insufficient mammary gland tissue. Other women have breasts that appear within normal limits yet do not lactate normally. Endocrine disruptors may underlie some of these cases but their impact on human milk production has not been well explored. Similarly, any problem with prolactin such as a deficiency in serum prolactin or receptor number, receptor resistance, or poor bioavailability or bioactivity could underlie some cases of insufficient lactation, yet these possibilities are rarely investigated. A weak or suppressed milk ejection reflex, often assumed to be psychosomatic, could be related to thyroid dysfunction or caused by downstream post-receptor pathway problems. In the absence of sufficient data regarding these situations, desperate mothers may turn to non-evidence-based remedies, sometimes at considerable cost and unknown risk. Research targeted to these clinical dilemmas is critical in order to develop evidence-based strategies and increase breastfeeding duration and success rates.