I have just seen a mother with 4 month old twins (born 32 weeks gest.) with
very low milk supply. Breastfeeding was going very well, good weight gains
until approximately 1 month ago.  Over a fortnight the weight gains were
half the usual gains. The mother was advised to give formula comps after
each feed - resulting in a plummeting of her milk supply, but huge weight
gains. Stopping the comps, expressing frequently, etc. the babies lost
weight over the next week.
When taking her history I discovered she suffers from hypothyroid and has
taken thyroxine for 5-7 years. Approx. one month ago, following blood
tests, her thryoxine dose was reduced from 150mg daily to 100mg daily. Can
this have had an effect on her milk supply?

Roslyn Draper - RM IBCLC -  Melbourne,Australia