Plant Hormones Are Circulating in Mammals

Cytokinins are plant hormones. They regulate cell division in leaves, roots and stems. They have no business being in your liver. And yet.

Cytokinins, previously regarded as plant-specific hormones, are now being detected systemically in multiple mammalian organs and blood. Researchers found them circulating at lower concentrations than in plants, but present all the same — and not just as passive dietary residue. Levels shift depending on diet and gut microbiota, with fasting and germ-free conditions reducing cytokinin pools, which points toward both external supply and something more regulated happening internally.

The assumption that these compounds belonged exclusively to the plant kingdom, where they govern growth and stress responses, is now looking overconfident. The body's own TRIT1 gene may be doing some of the work: this gene is associated with the synthesis of specific cytokinin types, and its presence suggests mammals don't rely solely on dietary sources but carry the genetic machinery to produce small amounts themselves. Researchers also identified cytokinin O-glucoside, an inactive storage form, which means the body isn't just absorbing these compounds — it appears to be managing them.

What cytokinins are actually doing in mammalian tissue remains an open question. The researchers stop well short of clinical claims. But the finding that plant hormones operate inside mammals through what looks like a regulated system, rather than simple dietary contamination, is the kind of result that tends to age interestingly.

Sixty years of plant biology textbooks just got a mammalian footnote.

Read the full story at Phys.org, June 19, 2026

Hot Take: The TRIT1 finding is the part worth watching: dietary exposure is a shrug, but endogenous production is a different conversation entirely.