WARNING: Naringin may block T4 → T3 conversion – overlooked interaction]
Hey everyone,
Just wanted to share something that doesn’t get much attention but might explain a lot of strange thyroid labs or stubborn fat loss issues, especially among those using thyroid support or metabolic enhancers.
---
The typical pattern:
In several cases I’ve seen (myself and others), bloodwork often shows:
High free T4
Low-normal free T3
Low or normal TSH
This is a textbook sign of poor peripheral conversion from T4 to T3, even though the thyroid itself is producing well (or getting exogenous support).
---
What I found:
Digging deeper, I came across scientific studies showing that naringin (a flavonoid found in grapefruit and many supplements, often dosed around 500 mg/day) can inhibit hepatic 5'-deiodinase, the enzyme responsible for converting T4 into active T3.
References:
1. ScienceDirect – Naringin suppresses hepatic 5′-deiodinase in hyperthyroid rats
2. PubMed – Antithyroid effect of naringin and related flavonoids (PMID: 25443740)
This results in lower T3, elevated T4, and a sluggish metabolism — even if your labs look “within range.”
---
Takeaway:
> If you’re taking naringin, or consuming a lot of grapefruit products, and your T4 is high but your T3 is disproportionately low, this might be the hidden reason.
This interaction is likely dose-dependent, and especially relevant for those using T4 therapy, cutting diets, or hormonal support where thyroid optimization is crucial.
---
Anyone else notice this pattern?
Would be great to hear feedback — this might be a highly overlooked piece in the thyroid/metabolic puzzle.
Hey everyone,
Just wanted to share something that doesn’t get much attention but might explain a lot of strange thyroid labs or stubborn fat loss issues, especially among those using thyroid support or metabolic enhancers.
---
The typical pattern:
In several cases I’ve seen (myself and others), bloodwork often shows:
High free T4
Low-normal free T3
Low or normal TSH
This is a textbook sign of poor peripheral conversion from T4 to T3, even though the thyroid itself is producing well (or getting exogenous support).
---
What I found:
Digging deeper, I came across scientific studies showing that naringin (a flavonoid found in grapefruit and many supplements, often dosed around 500 mg/day) can inhibit hepatic 5'-deiodinase, the enzyme responsible for converting T4 into active T3.
References:
1. ScienceDirect – Naringin suppresses hepatic 5′-deiodinase in hyperthyroid rats
2. PubMed – Antithyroid effect of naringin and related flavonoids (PMID: 25443740)
This results in lower T3, elevated T4, and a sluggish metabolism — even if your labs look “within range.”
---
Takeaway:
> If you’re taking naringin, or consuming a lot of grapefruit products, and your T4 is high but your T3 is disproportionately low, this might be the hidden reason.
This interaction is likely dose-dependent, and especially relevant for those using T4 therapy, cutting diets, or hormonal support where thyroid optimization is crucial.
---
Anyone else notice this pattern?
Would be great to hear feedback — this might be a highly overlooked piece in the thyroid/metabolic puzzle.
