Levothyroxine is used in:
L-thyroxine is thyroxine analogue. It has a a more sustained and uniform action. It is used in cretinsm and in hypothyroidism it contains T4 T3 medication is liothyronine which is used very rarely -only in myxedema coma (REF.Essential of medical pharmacology K D TRIPATHI 6 Edition, Page No - 248)
Thyroid storm
Cretinism
Endemic goiter
Grave's disease
Endocrinology