PCOS, Insulin Resistance, and Low Milk Supply - MALMS Study Review
Polycystic Ovarian Syndrome (PCOS) is a common endocrine disorder that is in essence a hormonal imbalance. Named for the polycystic ovaries often observed, characteristics of this syndrome include hyperandrogenism, anovulation, and insulin resistance. Anovulation contributes to difficulties conceiving. Insulin resistance is the hallmark of Type 2 Diabetes. Hyperandrogenism can be either biochemical (only detected on bloodwork) or associated with physical findings such as hirsutism or acne. The hormonal disruptions of PCOS can impact normal mammary glandular tissue development. Additionally, an association between insulin resistance in and of itself and low milk supply has been observed.
A syndrome is defined by the Oxford English Dictionary as “a group of symptoms which consistently occur together, or a condition characterized by a set of associated symptoms.” Affected individuals vary with their presentation and may experience few to all of the associated symptoms.
Not all women with PCOS experience difficulties conceiving. And not all women with PCOS experience difficulties with breastfeeding due to low milk supply. For the women who do, what can be done to help increase supply?
One of the challenges with addressing this question is teasing out the source of low milk supply. Did hormonal imbalances impact normal mammary gland development? Meaning, is the milk secreting glandular tissue not adequately developed to provide an adequate milk supply? Or, is current insulin resistance impairing milk production?
Metformin is a drug known to increase insulin sensitivity. It is used for the treatment of type 2 diabetes, and as a treatment of PCOS to address the insulin resistance component of PCOS. A study of out of Children’s Hospital Medical Center of Cincinnati looked to see if metformin could be used as a treatment to augment low milk supply in insulin resistant and pre-diabetic mothers.
Results of the Metformin to Augment Low Milk Supply (MALMS) Study became available in 2020. This small scale randomized control trial study did not show any statistical difference between the metformin receiving and placebo receiving group. Quite a bit of a disappointment that a trend was not readily apparent in this study. However, major limitations to this study were its small study size, and also the timeline of measuring outcomes (4 weeks).
In the breastfeeding medicine world, anecdotally providers note they have individual patients with PCOS who do report increased breast growth and increased milk supply over the course of several weeks to months after starting metformin. As with most galactogogues (including fenugreek and goat’s rue) it’s often trial and error to see if an individual is responsive or not.
Metformin as a drug is generally well tolerated, with the most common adverse effects being nausea, diarrhea, and abdominal discomfort. According to the Lactmed database, metformin levels in milk are low and a sizable study showed no adverse effects in breastfed infants.
When I have a mother with low milk supply with a history of PCOS, and/or a history of gestational diabetes, and especially if there is a personal history of type 2 diabetes or a strong family history of diabetes, I have a discussion with them about the potential benefits of starting metformin. As studies have yet to demonstrate its effectiveness, it’s important to set realistic expectations. However, based on the major limitations of the MALMS study, I think the major take-aways are that a larger study population and a longer follow-up time may be needed to detect significance.
