Thyroid hormone (TH) is known to have many beneficial effects on vital organs, 
but its extrapolation to be used therapeutically has been restricted by the fact 
that it does have concurrent adverse effects. Recent finding of various thyroid 
hormone receptors (TR) isoforms and their differential pattern of tissue 
distribution has regained interest in possible use of TH analogues in 
therapeutics. These findings were followed by search of compounds with 
isoform-specific or tissue-specific action on TR. Studying the 
structure-activity relationship of TR led to the development of compounds like 
GC1 and KB141, which preferentially act on the β1 isoform of TR. More recently, 
eprotirome was developed and has been studied in humans. It has shown to be 
effective in dyslipidemia by the lipid-lowering action of TH in the liver and 
also in obesity. Another compound, 3,5-diiodothyropropionic acid (DITPA), binds 
to both α- and β-type TRs with relatively low affinity and has been shown to be 
effective in heart failure (HF). In postinfarction models of HF and in a pilot 
clinical study, DITPA increased cardiac performance without affecting the heart 
rate. TR antagonists like NH3 can be used in thyrotoxicosis and cardiac 
arrhythmias. However, further larger clinical trials on some of these promising 
compounds and development of newer compounds with increased selectivity is 
required to achieve higher precision of action and avoid adverse effects seen 
with TH.