🏔️ Women’s High-Altitude Physiology Finally Gets Its Own Moonshot

A fellow mountain biker, who also happened to be a doctor, once offered to write my brother a prescription for Viagra (since he couldn’t write one for me) so I could take it before racing the Leadville 100 mountain bike race, on the theory that the same nitric oxide–mediated vasodilation that improves penile blood flow could also enhance systemic blood flow and help me race 104 mountainous miles in thin air. I said no, but it did make me think about what we knew—and didn’t know—about women and high-altitude performance.

Women now make up roughly 40% of the people in the mountains, yet less than 7% of published high‑altitude research actually looks at women–that number gets vanishingly small when you’re talking about 40+ women. A dedicated scoping review on menopause and high altitude identified just 10 studies and one abstract focused on menopausal women in hypoxic or high‑altitude conditions. That’s nowhere near enough to guide midlife athletes up big mountains with confidence.

That’s the gap Martha Tissot van Patot, PhD, and her ISHARE expedition team is setting out to climb into—literally. I sat down with Martha to learn more about this work, what they hope to achieve, and how women can get involved. 

The Big All-Women’s Expedition

ISHARE (International Sisters High Altitude Research Expedition) is the first all‑women high‑altitude medical research expedition. In September 2027, women from around the world will trek and climb in Nepal—from low altitude up to base camp around 5,000–6,000 meters (about 16,400–19,700 feet), with a smaller group attempting the 7,246‑meter (about 23,800‑foot) summit of Putha Hiunchuli—while collecting data on how women respond to altitude across the reproductive lifespan.

They’re enrolling women across pre‑, peri‑, and postmenopause and will classify participants by hormone levels, because that’s how transition actually looks in real life. They’re also including Sherpa women, who are genetically adapted to high altitude, alongside non‑Sherpa “lowlander” women, to start teasing out sex‑ and ancestry‑specific differences rather than continuing to extrapolate from Sherpa men.

Why This Matters for Midlife Women

The limited research we do have suggests menopause itself does not suddenly make women “bad” at altitude. A recent study using simulated altitude found that menopause, despite lowering estradiol and progesterone levels, did not impair women’s physiological responses to hypoxia or increase acute mountain sickness risk compared with younger women. Hypoxic ventilatory responses—how breathing ramps up as oxygen drops—were preserved. In broader aging work, women tend to maintain hypoxic ventilatory responses across the decades, while hypoxic cardiac responses decline with age, and older men show more pronounced declines in ventilatory response.

Other work looking at ventilatory and cardiac responses to hypoxic exercise across age and hormonal status reports that hormonal status (natural cycle, oral contraception, or menopausal hormone therapy) has limited impact on tolerance to altitude or on the risk of acute mountain sickness in the datasets studied.

But there are plenty of unanswered questions regarding real‑world symptoms, performance, and sleep at altitude.

There’s iron, which many of you already know is a complicated issue in women’s health and performance. Hypoxia and high altitude drive red blood cell production and alter iron metabolism. Reviews of high‑altitude residents show that long‑term adaptation alters hepcidin, ferritin, and erythropoiesis in ways that can help maintain functional iron status despite elevated red blood cell production. At the same time, endurance athletes are well‑known to struggle with iron deficiency because training increases iron losses and demand. Experimental work also suggests that chronic high‑altitude exposure can increase dietary iron absorption in young women through hypoxia‑mediated gut pathways, adding yet another layer to the picture.

Layer menopause onto that—where iron regulation and stores may change—and you get a “black box.” As Martha explained, we simply do not know how midlife women’s iron status and metabolism shape their performance, symptoms, and risk at altitude, or how that differs between Sherpa women and lowlanders. ISHARE’s profiling of iron metabolism hopes to shed some light on these unknowns. 

Then, of course, there’s sleep, which is already disrupted in menopause. At altitude, sleep becomes even more complicated thanks to periodic breathing and hypoxic apnea. When blood oxygen levels drop (hypoxia) during sleep, the brain triggers rapid, heavy breathing to recover. However, this hyperventilation blows off too much carbon dioxide. Because rising CO2 is what normally triggers the instinct to breathe, that drop causes the brain to temporarily stop breathing altogether (hypoxic apnea). This loop repeats all night, causing severe sleep fragmentation.

The official UIAA (Union Internationale des Associations d'Alpinisme–the global governing body for mountaineering and climbing) medical guidelines specifically state: "Both high altitude and age can increase sleep-disordered breathing, which can cause sleepiness, decreased exercise performance, cognitive dysfunction, and decision-making." While physically fit premenopausal women adapt well to hypoxia, aging and the sharp decline of progesterone (a natural respiratory stimulant) make sleep-disordered breathing and subsequent daytime cognitive fatigue an escalated risk for postmenopausal women.

Obviously, the results will directly help women who hike, climb, run, ride, swim, live, and otherwise perform at high altitude. But also, by treating high altitude as a stress test for women’s physiology, ISHARE may reveal how midlife women’s breathing, cardiac function, iron metabolism, and sleep respond under hypoxic stress—insights that are likely to inform how we think about similar systems during hard training, fatigue, and cardiometabolic risk at sea level, especially with regard to women.

How You Can be Part of It

Right now, there are two main ways you—or women in your circle—can plug into the ISHARE mission. 

• Apply to trek or climb
  Applications for trekkers and climbers are open on isharemountains.org through the end of July. Costs are roughly $9,000–$11,000 depending on whether you’re trekking to base camp (around 16,400–19,700 feet) or attempting the 23,800‑foot summit. A portion of each participant’s fee goes into a pool that funds participation for Sherpa women and Nepalese women scientists. Hormone therapy is explicitly not an exclusion: They want women on HRT included, because that’s real‑world physiology and those data matter.

• Support and amplify the mission
  ISHARE is entirely privately funded and uses small, global donations and broad visibility to show corporations and foundations that women’s altitude health is worth investing in. Following and sharing their channels—isharemountains.org and Instagram @ishare.2027—helps build that international support base and keeps pressure on the system to prioritize sex‑specific mountain medicine.

I’ll be following along—and sharing what they discover—as this historic all‑women mountain medicine moonshot takes off.