Bioidentical Hormones & Cancer: Time for Clarity

Something that has been taught and repeated for more than two decades does not simply disappear from medical and public awareness overnight.

In my daily practice, I continue to observe how deeply many women still fear hormone replacement therapy. This is not because they have had negative experiences themselves, but because a certain narrative has taken root over the years.

• Hormones are risky.
• Hormones cause cancer.
• Hormones are best avoided.

These beliefs run deep. Often unconsciously. They continue to shape decisions to this day.

A Generation Without Hormone Therapy (2002–2025):

Following the publication of the Women's Health Initiative (WHI) study in 2002 [1], there was a significant global change in the treatment of women experiencing perimenopause and menopause.

In the years that followed, the use of hormone therapy declined dramatically. This was not because it had lost its effectiveness. Fear became the driving force.

Between 2002 and 2025, nearly an entire generation of women went without adequate hormonal support, despite having significant symptoms and clear medical indications. For countless women, this meant:

• years of untreated menopausal symptoms;
• an increased risk of osteoporosis and fractures [4];
• a rise in cardiovascular disease;
• cognitive changes;
• a noticeable decline in quality of life.

Today, experts are increasingly speaking openly about this unnecessary suffering. This was not because treatment did not exist, but because there was a fear of using it.

Why the fear persists

Even though scientific evidence has evolved considerably, the central message from the early 2000s still lingers.

'Hormones are dangerous.'

This view has been perpetuated for years through medical education, clinical practice, media coverage and personal conversations.

Two generations of healthcare providers received little to no structured training in modern menopause medicine. Hormones were considered delicate, controversial or a last resort.

To this day, many patients tell me that their symptoms are not taken seriously, or are only superficially treated, without a proper hormonal assessment or exploration of the underlying causes.

The WHI Study: What Was Actually Studied?

One key point that remains widely misunderstood is that the WHI study did not examine modern hormone therapy. It investigated:

• oral conjugated equine oestrogens combined with a synthetic progestin (medroxyprogesterone acetate);
• in women with an average age of 63;
• often 10 to 15 years past menopause.

It did not study:

• bioidentical estradiol;
• transdermal hormone therapy, such as patches, gels or sprays;
• bioidentical progesterone.

Therefore, the sweeping conclusion that 'hormones are dangerous' was based on a significant oversimplification. This oversimplification had far-reaching consequences.

Bioidentical hormones and the birth control pill

An important distinction is often overlooked. The birth control pill contains synthetic progestins, not bioidentical progesterone.

Large-scale epidemiological studies, including Danish research involving over 1.8 million women, have revealed that certain synthetic progestins may increase the risk of cancer.

This risk is not attributable to oestradiol itself, but rather to the altered chemical structure of progestins. Bioidentical progesterone behaves differently in the body.

FDA Update 2025: A Medical Turning Point

On 25 November 2025, the U.S. Food and Drug Administration released a comprehensive update [2] on hormone therapy.

Under the title 'Updated Labelling for Menopausal Hormone Therapy', previous blanket warnings were revised and differentiated. I consider this step by the FDA [3] long overdue and, at the same time, an important turning point.

The FDA now explicitly emphasises:

• the necessity of an individualised risk–benefit assessment;
• a clear distinction between:

- local therapy, such as vaginal oestrogen;

- systemic therapy;

- transdermal application;

• the relevance of the timing hypothesis;
• support for personalised hormone therapy.

The goal of this revision is to reduce diffuse fears and enable evidence-based decision-making.

Modern hormone therapy: today

Today's hormone therapy differs fundamentally from earlier approaches. It is based on:

• bioidentical 17β-estradiol, preferably administered transdermally as a patch, gel or spray;
• bioidentical progesterone;
• individualised dosing;
• regular medical supervision.

When used appropriately, particularly before the age of 60 or within ten years of menopause, an individualised hormone therapy regimen can:

• protect bone health
• support cardiovascular function
• help stabilise cognitive performance
• significantly improve sleep, mood, and overall quality of life

Responsibility towards future generations

The impact of the WHI study does not end with updated guidelines or regulatory changes.

Medical beliefs formed over decades do not shift overnight. Without targeted education, there is a real risk that future generations of women will continue to be underserved, even though medical options have long been available.

Modern menopause medicine therefore means more than just treatment. It also requires education, differentiation and greater awareness.

A final thought

The central question today is no longer “Are hormones dangerous?”

The more important questions are:

• Which hormones? At what time? In what form? And for which woman?

The consequences of the WHI study do not end in 2025. What shapes one generation often continues to influence those that follow.