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.