When Hormones Hide the Truth: What Parkinson's Research Is Finally Beginning to Reveal

I bought this at the Frank Lloyd Wright Museum after the WPC Congress in Phoenix, Arizona.

Sometimes the most important discoveries aren't about finding new answers.

They're about asking better questions.

A large Latin American study recently reported that men and women experience similar rates of levodopa-induced dyskinesia (LID). At first glance, the finding seems reassuring. It suggests that sex may not play a major role in one of Parkinson's most challenging treatment complications.

But for many women living with Parkinson's, particularly those diagnosed at a younger age, that conclusion doesn't quite fit their experience.

Discussing research at Women with PD roundtable at WPC 2026

For years, women have reported changes in symptoms during their menstrual cycle, pregnancy, perimenopause and menopause. Many describe fluctuations that cannot be explained by medication timing alone.

So what happens when we look beyond sex and start looking at hormonal stage?

A Different Lens on Parkinson's

Through My Moves Matter, in collaboration with researchers at University College Cork, we conducted what we believe is one of the first large-scale digital studies specifically designed to explore women's experiences of Parkinson's disease.

Nearly 500 women contributed symptom and medication data through the My Moves Matter platform.

When we analysed the results, a fascinating pattern emerged. Women who were still menstruating reported higher levels of stiffness and dyskinesia, while postmenopausal women reported more balance difficulties.

The differences were consistent enough to raise an important question: Could hormonal stage influence how Parkinson's symptoms are experienced?

Looking Beyond Sex

Traditionally, research has compared men and women. But women are not a single biological group.

My fellow Parkinson's advocates at WPC 2026.

A woman in her 30s, a woman in perimenopause, and a woman 15 years beyond menopause are living in very different hormonal environments.

When all women are grouped together, important biological signals may be lost.

Our findings suggest that menopausal status may reveal patterns that are not apparent when researchers simply compare males versus females.

Could Hormones Influence Dyskinesia?

We know that sex hormones interact closely with dopamine systems in the brain.

Researchers have proposed that oestrogen may influence dopamine signalling, medication response and motor complications, although the exact mechanisms remain incompletely understood.

One possibility is that hormonal fluctuations during reproductive years may affect how the brain responds to levodopa. Another is that hormonal stability may be just as important as hormone levels themselves.

Interestingly, in a smaller subgroup analysis, women using hormone replacement therapy appeared to report lower dyskinesia levels than expected. While the numbers were too small to draw firm conclusions, the finding raises intriguing questions about whether stable hormone exposure could influence symptom patterns differently from natural hormonal fluctuations.

These are questions that deserve much closer investigation.

Are We Missing Something in Traditional Research?

One possible explanation for why some large studies find little or no sex difference in dyskinesia is that age of onset, hormonal stage and sex are often analysed separately rather than together.

Younger-onset Parkinson's disease is associated with a higher risk of dyskinesia.

Hormonal status changes dramatically across a woman's lifetime. When these factors are combined into broad averages, important patterns may become harder to detect.

Statisticians refer to this phenomenon as Simpson's paradox, where meaningful differences within subgroups can disappear when data are pooled together.

Whether this explains findings from previous Parkinson's studies remains to be tested, but it highlights the importance of looking beyond simple male-versus-female comparisons.

Why This Matters

The goal is not to prove that hormones cause dyskinesia. The goal is to understand why women often experience Parkinson's differently.

For decades, women have reported symptom changes linked to menstruation, pregnancy, perimenopause and menopause. Yet these experiences have rarely been incorporated into clinical trials, treatment guidelines or routine care.

If hormonal stage influences symptom patterns, medication response or quality of life, then it deserves far greater attention from researchers and clinicians alike.

The Beginning, Not the End

For me, this is one of the most exciting aspects of the My Moves Matter journey.

What started as a way of helping people track their symptoms has become a platform capable of generating entirely new research questions.

The women who contributed their experiences to this study didn't just provide data. They helped shine a light on an area of Parkinson's research that has been overlooked for far too long.

A fabulous afternoon at the Frank Lloyd Wright Museum which sparked much discussion about sex & gender differences in PD

We're only beginning to understand the relationship between hormones and Parkinson's disease. But one thing is becoming increasingly clear:

If we want to understand women with Parkinson's, we need to stop treating women as a single group and start recognising the biological transitions that shape their experience.

Because sometimes the most important findings aren't hidden in the data.

They're hidden in the averages.

References

Chaparro‑Solano, H. M., Teixeira‑dos‑Santos, D., Waldo, E., Leal, T. P., Inca‑Martinez, M., Alcauter, S., Medina‑Rivera, A., Ruiz‑Contreras, A. E., Cornejo‑Olivas, M., Mejia‑Rojas, K., Armas, C., Chana‑Cuevas, P., Rojas, N., Orozco, J. L., Muñoz Ospina, B., Aguillon, D., Buritica, O., Moreno Masmela, S., Tumas, V., … Mata, I. F. (2026). Levodopa‑Induced Dyskinesia in Latin America: Prevalence and Associated Clinical Factors in the LARGE‑PD Cohort. Journal of Parkinson’s Disease, 16(4), 723–735. https://doi.org/10.1177/1877718X261431204

Moore S, Collins Stack L, Flanagan R, Reinbacher R, Lavelle A, Sullivan A.   Tracking symptoms and medications in women with Parkinson’s disease. Parkinsonism Relat Disord. 2026;13(S1):P39.21. https://journals.sagepub.com/doi/10.1177/1877718X261451755