THC and CBD Directly Interfere With Calcium Channels in Human Sperm, Potentially Affecting Fertility | Research

The takeaway

THC and CBD directly affected CatSper calcium channels in human sperm — the same channels essential for sperm activation by progesterone — with THC also altering sperm function in lab tests, raising concerns about cannabis effects on male fertility.

Reproductive endocrinologists, urologists, couples trying to conceive, and men who use cannabis.

What the researchers found

THC and CBD affected the sperm-specific CatSper calcium channel, suppressing its activation by progesterone (P4) and prostaglandin E1 (PGE1). THC also altered human sperm function in vitro. These effects occurred through direct action on the ion channel rather than through cannabinoid receptors.

Why it matters

CatSper is the primary calcium channel driving sperm toward the egg — it's essential for fertilization. If THC and CBD suppress this channel, cannabis use by men trying to conceive could directly impair their fertility at the cellular level.

The numbers in context

THC and CBD both suppressed CatSper activation by progesterone (P4) and prostaglandin E1 (PGE1). THC altered sperm function in vitro. Effects occurred through direct ion channel action, not cannabinoid receptors.

How the study worked

In vitro study testing THC, CBD, and their major metabolites on calcium influx via CatSper channels in human spermatozoa. Calcium signaling measured in response to progesterone and prostaglandin stimulation with and without cannabinoid pre-treatment.

What this study cannot tell us

In vitro study — lab conditions may not reflect concentrations in reproductive tract after cannabis use. Metabolite effects may differ from parent compounds in vivo. Only acute effects tested. Human studies on fertility outcomes needed.

How to read the evidence

In vitro mechanistic study providing molecular evidence, but concentrations and conditions may not reflect in vivo exposure during cannabis use.

When this study was published

Published 2025.

The bigger picture

Previous studies have shown cannabis can affect semen parameters (count, motility), but the mechanism was unclear. This study identifies a specific molecular target — the CatSper channel — providing the first direct evidence of how phytocannabinoids may impair the fertilization process itself.

Questions still open

What concentration of THC/CBD reaches the reproductive tract after cannabis use? Is the CatSper suppression reversible with cannabis cessation? Could this mechanism explain some cases of unexplained male infertility in cannabis users?

Common questions

Can cannabis affect male fertility?

This study provides direct evidence that THC and CBD suppress the CatSper calcium channel that sperm need for fertilization. While this is lab-based evidence, men trying to conceive may want to discuss cannabis use with their fertility specialist.

Does CBD also affect sperm, not just THC?

Yes — both THC and CBD suppressed CatSper channel activation by progesterone. This means even non-intoxicating CBD products could potentially affect sperm function, though real-world concentrations reaching the reproductive tract are unknown.

Read the original research

The major phytocannabinoids, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), affect the function of CatSper calcium channels in human sperm.

Human reproduction (Oxford, England), 40(5), 796-807

View on PubMed ↗Publisher’s paper ↗

Citation

Wehrli, Lydia; Altevogt, Hannah; Brenker, Christoph; Zufferey, Fanny; Rossier, Michel F; Strünker, Timo; Nef, Serge; Rahban, Rita. (2025). The major phytocannabinoids, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), affect the function of CatSper calcium channels in human sperm.. Human reproduction (Oxford, England), 40(5), 796-807. https://doi.org/10.1093/humrep/deaf020