Julie,
Synthroid is one drug that is notorious for wide swings in bioavailability
from batch to batch.  Postpartum is also a time of metabolic change.  When has
this mom had her synthroid dosage adjusted last?  She could need a higher dose
to make adequate milk.  Is she having other symptoms that might confirm or
refute the need for more medication?
Catherine Watson GEnna, IBCLC  NYC  [log in to unmask]