PMOS Awareness Month: Explaining Insulin Resistance

It's Polyendocrine Metabolic Ovarian Syndrome (PMOS) Awareness Month and at Lena, we believe the dissemination of evidence-based and current literature supports women in making the best decisions about their health, so we wanted to share our latest findings, from our medical expert Dr Rachel Denham. PMOS is a complex condition which has recently been renamed from PCOS to more fully encapsulate the wide range of lived experiences that can be felt by patients. To find out exactly what PMOS is and what it looks like, check out our latest blog post here. 

What Is Insulin Resistance?

To first understand insulin resistance, I'm going to explain what insulin is and what happens when it is functioning normally.

Insulin is a hormone produced by the pancreas, an endocrine gland in your abdomen. Insulin is released from the pancreas after we have eaten, and its job is to stimulate the liver and tissues to take up sugar and convert it to energy.

If insulin or its system is not functioning properly, then sugar is not transported into cells and it raises your blood glucose levels. If your blood sugar is too high for an extended period of time, this can lead to Prediabetes and then eventually Type 2 Diabetes*, which is linked to cardiovascular disease, obesity, metabolic syndrome, non-alcoholic fatty liver disease and stroke.

The process of insulin resistance can be likened to a postal delivery service.

• Insulin, the postal delivery person, is trying to post glucose through the door of your cells.
• In insulin resistance, the doors won't open (pretty much).
• This is usually a consequence of the delivery person knocking too often prior (like bringing you far too much spam mail), and so the door has decided to stop opening. 
• Without the door opening, all of the post (glucose) remains in the postal system (your blood) and levels of it become difficult for the system to manage (your body starts to struggle and tissues are damaged by raised glucose).

In reality, when too much glucose is consumed through our diets, our blood sugar is raised more often, meaning that insulin has to work more, and harder, to get that glucose into the cells. Over time, the cells stop responding to insulin as they become less sensitive to it. You can have too much of a good thing!

*Type 1 Diabetes is when the body does not produce sufficient insulin and requires you to take insulin for the rest of your life as a medication, typically discovered in young children or teenagers. Type 2 Diabetes is when insulin is not working properly or there is not enough of it, often discovered in later life and can be induced by diet, pregnancy or other complications.

Why Does It Matter In PMOS?

Insulin resistance affects 65-95% of women with PMOS, they aren't just linked, insulin resistance is a physiological driver of the condition. Here's why that matters:

• Insulin directly increases testosterone (an androgen) production in the ovaries, which is one of the diagnostic criteria for PMOS. 
• Raised insulin levels can affect egg quality and even delay ovulation, causing fertility problems which are often experienced by those with PMOS.
• Raised insulin can also reduce levels of Sex-Hormone Binding Globulin (SHBG) which normally reduces levels of testosterone. Without SHBG, levels of testosterone can continue to climb, worsening PMOS.
• High levels of insulin disrupt regular brain messaging systems, most importantly in the hypothalamic-pituitary axis (a key hormonal signalling system). This can lead to high levels of Luteinizing Hormone (LH), which can disrupt ovulation further and lead to increased androgen output by the ovaries.

All of the above contributes to the worsening of PMOS, particularly the raised androgen levels, which can lead to some of the key hallmark symptoms of hair growth, acne and lack of ovulation.

How Does Insulin Resistance Influence Treatment of PMOS?

It's important to say that these treatments are more often considered for patients who have a raised BMI or cases in which the prescribing doctor suspects that losing weight will support the management of the condition. These are not given to every patient. Because of the importance of addressing insulin, patients with PMOS have been prescribed medications such as Metformin or GLP-1 agonists, which are typically used in diabetes treatments. Here's a quick overview of why they are used:

Metformin

• According to a 2023 review, the use of Metformin has been shown to reduce insulin resistance and restore some hormonal rhythm, potentially leading to the return of ovulation and therefore improving fertility outcomes for PMOS patients. However, the study notes that wider and more inclusive studies are needed to consolidate the understanding of the long-term use of metformin in PMOS.
  

Semaglutide (GLP1-agonist)

• A 2026 review described how the use of Semaglutide has been linked to improved reproductive outcomes for PMOS patients, through reducing insulin resistance and testosterone production.

Want To Learn More?

Throughout September, we'll be breaking down the science of PMOS and helping you to understand the condition a little bit more each week. If you've enjoyed this article, please check out the Lena blog for more evidence-based, expert-led content. 

Written and edited by Dr Rachel Denham, a trained medic and Women's Health Practitioner, who has worked across the charity and humanitarian sector and now specialises in women's health. Rachel is the creator of Bloody Nora, a women's health and wellbeing zine that fuses storytelling, art and science.