Some people are told their thyroid tests are “normal”, yet they still feel tired, sluggish, foggy or unable to lose weight. One often-overlooked reason is how well your body converts T4 (thyroxine) into the hormone T3 (active form).

When the body reduces T4→T3 conversion

Research shows this can happen for several clinically validated reasons:

• Stress, inflammation and illness: The body lowers T3 during recovery to preserve energy.
• Fasting, undereating or over-exercising: Kilojoule or nutrient deficits reduce thyroid activation.
• Low selenium status: The enzymes that convert T4 to T3 require selenium to function.

Why this matters

Even with “normal” TSH and T4 levels, low T3 levels can contribute to symptoms like:

• Fatigue 
• Low mood & brain fog
• Weight changes
• Cold intolerance
• Dry skin

A Naturopathic approach

At our clinic, we look beyond basic thyroid results and assess how you are feeling and the whole picture — inflammation, nutrient status, stress levels, mitochondrial health, medications, gut function and underlying drivers that influence hormone conversion.

If you suspect your thyroid isn’t performing at its best, or taking Levothyroxine (T4) and still feeling sluggish, we can help you uncover what’s really going on and create a personalised plan to help restore balance and feel brighter. 

Your thyroid is more than a number. It’s a finely tuned system that responds to your whole-body environment — and we can help you bring it back into balance.

Contact us on 08 9381 1468 for further information or to book a consultation with our experienced team. 

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References

• Van Uytfanghe et al. (2023). Thyroid, 33(9), 1013-1028.
• Mazza, A. D. (2025). Cureus, 17(8).

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