An overlooked fat-derived hormone may drive higher breast cancer death risk in postmenopausal women with obesity, an analysis suggests.

The review identifies oestrone, a form of oestrogen produced in fat tissue, as a major driver of oestrogen receptor positive (ER+) breast cancer, the most common and deadly form of the disease in postmenopausal women.

ER+ means the cancer grows in response to oestrogen. It also raises the possibility that treatment could be improved with the addition of weight-loss drugs known as GLP-1 receptor agonists.

The analysis was led by Joyce Slingerland, who co-leads the Cancer Host Interaction Program at Georgetown University’s Lombardi Comprehensive Cancer Center in the US.

She said postmenopausal women with obesity are more likely to be diagnosed with ER+ breast cancer and are two to three times more likely to die from it.

Slingerland said: “That’s particularly concerning because it’s estimated that obesity will affect nearly half of women in the United States by the end of the decade.”

Before menopause, the most abundant oestrogen in women is 17β-oestradiol, produced primarily by the ovaries.

After menopause, its levels fall dramatically and oestrone becomes the most abundant form circulating in the blood.

Despite their similar chemical structure, the research suggests these two forms of oestrogen behave very differently.

While 17β-oestradiol turns on genes that reduce inflammation, oestrone does the opposite, activating genes that trigger intense inflammatory activity.

In the context of obesity, levels of oestrone are two to four times higher in fat, breast and other tissues.

The analysis suggests these elevated levels set off a cascade that causes precancerous changes and activates cancer-fuelling genes.

Previous research by the team showed that oestrone-fuelled inflammation activates genes involved in a process that promotes cancer spread.

When researchers treated obese mice with ER+ breast cancer with oestrone, their tumours grew faster and rapidly spread throughout the body compared with mice treated with 17β-oestradiol.

Slingerland said: “Our work has provided some of the causal links between oestrone and the worse outcomes seen in postmenopausal women with ER-positive breast cancer who are obese.

“Simply put, these two oestrogens are not equal to each other.”

The author argues that clinical studies of GLP-1 drugs in women with ER+ breast cancer who have obesity are a logical next step.

Slingerland said: “The GLP-1 drugs have revolutionised weight loss.

“Because of oestrone’s powerful inflammatory effects in fat, there’s real potential that, by inducing weight loss, GLP-1 drugs can pump the brakes on oestrone’s cancer-fuelling behaviour.”

Fertility finance platform Sunfish has expanded its partnership with US clinic network Ivy Fertility to support patients across all 28 of its locations.

The deal will give all Ivy patients access to Sunfish’s Financial Hub, a platform designed to help people navigate the costs of medically assisted fertility care, as well as its loan marketplace and network of partner lenders.

Select clinics will also offer Sunfish’s IVF Success Program, which uses biodata to create customised flat-fee IVF bundles. IVF (in vitro fertilisation) involves fertilising an egg in a lab and transferring the embryo to the uterus.

Angela Rastegar, chief executive and co-founder of Sunfish, said: “Ivy was one of our first clinic partners, and three years and hundreds of patients later, we’re thrilled to support even more families on their fertility journeys.

“As someone who has been through the process myself, I have always believed that IVF shouldn’t feel like a financial gamble, and now at Sunfish, we’re using data, AI, and design to make care more accessible and easier to navigate.

“This combination of predictive analytics and financial protection, paired with the exceptional patient care Ivy offers, is transforming how families and clinics think about fertility and financing.”

Sunfish says its approach is proving effective.

According to the company, 70.8 per cent of embryo transfers among its patients have resulted in a successful pregnancy and graduation to an obstetrician, compared with a national average of 54.3 per cent.

The firm also says twice as many patients without insurance have been able to start treatment at clinics offering its programme.

For patients using Sunfish’s IVF Success Program, the company’s predictive model uses AI and biodata to estimate the total cost from first consultation through to delivery.

The firm offers a cost guarantee and partial refund if treatment is unsuccessful.

Constance Rapson, chief growth officer at Ivy Fertility, said: “As a long-time Sunfish partner, we’ve seen how they are using new technology to make the patient experience excellent by providing greater financial support and clarity, ultimately helping more people go home with a baby.

“We’re excited to bring this innovative care to all of our patients.”

Financial barriers remain a significant obstacle to fertility treatment in the US.

Data suggests 54-65 per cent of prospective patients drop out of treatment, often due to financial strain.

Sunfish also announced an expansion of its Sunfish Cares initiative to all of its clinic partners, which contributes at least US$1,000 towards every new IVF Success Program patient at participating clinics through to the end of the year.