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Liothyronine treatment in hypothyroidism. Dr John Clark. Thyroid Treatment. Synthetic thyroxine available in 1950s Previously used porcine thyroid extracts which were not physiological Porcine ratio T4:T3 is 4:1 Human ratio T4:T3 is 14:1. Over-replacement.
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Liothyronine treatment in hypothyroidism Dr John Clark
Thyroid Treatment • Synthetic thyroxine available in 1950s • Previously used porcine thyroid extracts which were not physiological • Porcine ratio T4:T3 is 4:1 • Human ratio T4:T3 is 14:1
Over-replacement • Occurred in the 1970s and 80s with thyroxine alone • Now have more accurate TSH level • Predisposed to atrial fibrillation + osteoporosis
On Thyroxine but still symptomatic • Have FT4 and TSH returned to normal? • If TFTs normal check for other pathology • Particularly other auto-immune conditions • Was TSH definitely elevated at diagnosis? (remember pituitary disease) • Consider checking FT3 if nothing else present to explain symptoms
Normal FT4 and TSH but low FT3(on thyroxine alone) • No other pathology and patient has significant symptoms • Consider referral to Endocrine Service to discuss possible combination therapy (T4 + T3)
Normal FT4, FT3 +TSH(on thyroxine alone) • No other pathology and patient has significant symptoms • Are patients symptoms “psychological” rather than endocrine? • Possibly refer to Endocrine Service to discuss combination therapy (T4 + T3)
Combination Therapy • Only do as a trial – supervised by endocrinologist • Usually require 25-50ug reduction in thyroxine • Add in liothyronine 5ug bd • After 6 weeks are all TFTs normal and is patient feeling any better?
Combination Therapy • Evidence of benefit in trials – none • British Thyroid Association 2016 “Can do in very small number of appropriately selected patients, who have unambiguously not benefitted from thyroxine treatment”
Cost • Liothyronine was £5/month, now £400/month • Reason? • As a consequence I very rarely prescribe it • But Europe! • Armour extract
Replacing liothyronine with thyroxine • Clinically relatively straightforward • Psychologically very difficult - dependancy
Summary • 99% of hypothyroid patients will do well on thyroxine treatment alone • The remaining 1% - liothyronine “unavailable” due to cost - ? Europe • Can patients already on liothyronine have it replaced with thyroxine? Yes – if patient agrees.