What is IGT?

Parents who follow me often arrive here after weeks (or months) of doing everything “right”. They have a collection of flange sizes and pumps and have gone through (or are currently experiencing) the torture of triple-feeding. They've power pumped their way through entire netflix series, and supplemented with a trove of "we promise this will increase your supply" supplements. They've gone to the chiropractor and the pediatric dentist and everyone says it's all fine- or worse: "just pump more," and yet STILL milk supply won't budge, no matter how much we want it or what more we do. Sometimes we can do everything "right," but still struggle with milk supply.

When this happens, one possible explanation is primary low milk supply (PLMS), which is defined as the inability to exclusively breastfeed due to underlying maternal conditions (Whelan, 2025). The prevalence of PLMS is estimated to affect up to 10-15% of those during lactation (Lee, 2016).

IGT, or Insufficient Glandular Tissue is one such condition that can cause result in primary low milk supply.

I could write a whoooole book about the misinformation that surrounds IGT and PLMS (maybe someday I will, when I'm not knee-deep in child-rearing my three wildlings) but I can confirm, in fact, that misunderstanding and misinformation regarding IGT is rampant. Let's talk about IGT is and isn't.

IGT is characterized by the inability to exclusively breastfeed due to a lack of milk-making cells (called alveoli) in the breasts. Alveoli develop in clusters called lobes or lobules, and these lobes are also known as "glandular tissue," hence the name "insufficient" glandular tissue. Sometimes you hear that people with IGT "might be able to able to exclusively breastfeed." This is incorrect- if you can breastfeed exclusively, you do nothave IGT (the volume of alveoli in your breasts is sufficient to support exclusive breastfeeding). With IGT, you could nurse or pump 40 times a day and STILL it is not enough to support exclusive breastfeeding. There just aren't enough milk-making factories available to support it. It doesn't have to do with effort, it has to do with anatomy and biology.

Is Breast Hypoplasia IGT?

Sometimes you hear the term breast (or mammary) hypoplasia used interchangably with IGT. "Hypo" meaning under and "plasia" meaning growth or formation. While "breast hypoplasia" is a term with less negative connotation, much of the focus on breast hypoplasia in research surrounds anatomical characteristics of the breasts which can be observed with the naked eye. These include wide spacing at breast base, conical or tubular breast shape, and obvious underdevelopment in (at least) the lower inner quadrant of the breast, with potential underdevelopment in up to all 4 quadrants.

The issue with using interchangable terms of "IGT" and "breast hypoplasia" is that hypoplasia has come to refer to the appearance of specific external breast features and IGT isn't always obvious by appearance alone, especially to those with less familiarity of it. Additionally, someone may present with some degree of breast hypoplasia but have sufficient glandular tissue to support exclusive breastfeeding. This is because the breasts aren't just glandular tissue, they're also comprised of a lot of adipose (fat) tissue. Especially in breasts with a larger volume of fat tissue, lower glandular tissue can be less obvious and the opposite is also true. (This is why I tell lactation consultants that unless we have x-ray vision and can see the cells inside someone's breasts, we shouldn't make assumptions based on physical appearance alone).

Features Associated With Increased Risk of IGT

Currently, there is no clinical guideline for diagnosing IGT (afterall, we're still arguing about what to even call it). But there are risk factors associated with IGT that can alert us to the possibility of its presence and signal need for more thorough assessment.

Research and clinical observation have identified certain features that appear more commonly among parents later found to have IGT (Huggins et al., 2000; Marasco, West & Kent, 2020):

• minimal breast growth during puberty or pregnancy

• lack of engorgement when milk is expected to “come in”

  Symptoms of breast hypoplasia, including:

• widely spaced breasts (greater than 1.5" apart)

• tubular or elongated shape

• marked asymmetry

• disproportionately large or bulbous areolae

  
  

IGT breasts with symptoms of hypoplasia

In all the years I've been supporting families, I will tell you that the biggest red flag for potential IGT when we're discussing possible PLMS causes is when I hear someone say something along the lines of "my breasts didn't grow at all when I was pregnant and I kept being told my milk would come in and I'd feel full.. but it just never happened. I don't feel any difference."

And what's worse... many of these parents have already seen lacation consultants and healthcare providers who never mentioned the possibility (or existence) of IGT. This is due, in part, to a lack of provider education surrounding the condition.

Causes of IGT

IGT is either congenital, meaning you are born with it, or it can be aquired, meaning it developed after birth (usually in puberty and/or pregnancy). (Kam, 2024).

Congenital Cause

The congenital cause of IGT is believed to be attributed to "tuberous breast deformity," which is a connective tissue constriction within the breast, present from birth, that results in development of breast hypoplasia and IGT. When IGT is caused by this constriction, we often see breasts that have more obvious signs of hypoplasia.

Acquired Cause

Acquired causes of IGT can vary, but mainly revolve around underlying hormonal and metabolic influences, such as PCOS and/or symptoms of insulin resistance and thyroid dysfunction. Luteal phase defect is another condition reported to be attributed to IGT in some, as well. Other theorized factors include nutrient deficiencies, toxin exposure and breast injury during puberty or adolescence. The mammary glands are organs that revolve around branching morphogenesis, meaning glandular tissue builds off of itself, like a growing tree. When there's an interruption to that growth, especially in puberty, it results in less glandular tissue.

Can Parents With IGT Still Breastfeed?

Yes, if the parent desires to, though not exclusively. Early detection promotes more positive outcomes in feeding and maternal mental health.

Families affected by IGT may choose to continue breastfeeding through various practices, including:

• combination-feed with formula or donor milk

• use at-breast supplementers like the Lact-aid to simplify early breastfeeding

• shift focus to protecting the nursing relationship

• pump strategically to maintain production

• emphasize long-term sustainability rather than exclusivity
  

One of the most difficult components of IGT is how it takes away the picture of infancy for our child that we envisioned. For so many of us, we had clear expectations based on all we were told would happen and it seemed like exclusive breastfeeding was just a matter of work and commitment. When our work and commitment can't provide that, especially when we don't have informed and adequate support- it can impact our self-image, increase feeding anxiety and leave us feeling isolated in our experience.

There are a lot of ways to succeed in breastfeeding that don't depend on milk supply or how much/how little we produce. Success also includes infant growth, parental mental health, informed decision-making, and feeding plans that remain workable over time. It means nurturing our children through means accessible to us that promote bonding and discovering what it means to provide.

When to Seek Specialized Evaluation

When supply remains low despite optimized feeding or pumping frequency, latch, pump fit, and overnight milk removal, it's worth getting individualized support to assess for possible primary low supply causes, including IGT.

Evaluation should include:

• detailed lactation history

• infant exam: oral and body

• breast exam, including history of growth

• infant feeding history, including weight gain

• supplementation history and practices

• pumping practices including pump and flange use

• laboratory screening (thyroid function, prolactin, iron status, glucose/insulin markers, androgen levels, etc)

  
  

A comprehensive approach helps distinguish IGT from other PLMS causes and other sources of low milk supply (secondary low milk supply causes).

A Final Word

If you are reading this because you fear your body has limits around milk production, know this:

IGT is not something you caused.

Human bodies vary. Lactation capacity varies. Worth does not vary with output. Families deserve honest information, compassionate counseling, and feeding plans rooted in physiology, not pressure or shame. If you need help, please reach out. I'd be honored to support you.

References

Whelan, C., et al. (2025). Breastfeeding with primary low milk supply: A phenomenological exploration of mothers’ lived experiences of postnatal breastfeeding support. International Breastfeeding Journal, 20(1), 7. https://doi.org/10.1186/s13006-025-00699-4

Lee, S., & Kelleher, S. L. (2016). Biological underpinnings of breastfeeding challenges: The role of genetics, diet, and environment on lactation physiology. American Journal of Physiology – Endocrinology and Metabolism, 311(2), E405–E422.

Huggins, K., Petok, E., & Mireles, O. (2000). Markers of lactation insufficiency: A study of 34 mothers. Current Issues in Clinical Lactation.

Marasco, L., West, D., & Kent, J. (2020). Breastfeeding difficulties related to insufficient glandular tissue. Journal of Human Lactation.

Neifert, M. R. (2001). Prevention of breastfeeding tragedies. Pediatric Clinics of North America, 48(2), 273–297.

Neville, M. C., Morton, J., & Umemura, S. (2001). Lactogenesis: The transition from pregnancy to lactation. Pediatric Clinics of North America, 48(1), 35–52.

Nommsen-Rivers, L. A. (2016). Does insulin explain the relation between maternal obesity and poor lactation outcomes? Journal of Mammary Gland Biology and Neoplasia, 21, 181–190.

Kirigin Biloš, L., et al. (2017). Insulin resistance and breastfeeding. Journal of Obstetrics and Gynaecology, 37(6), 780–784.

Kam, R. L., et al. (2024). Breast hypoplasia markers among women who report insufficient milk production: A retrospective online survey. PLOS ONE, 19(2), e0299642. https://doi.org/10.1371/journal.pone.0299642