I have followed a couple of mothers with MS.  One with two babies.
Milk supply was terrific, though confidence was not.

The hyperthyroid-hypothyroid is a result of an inflammation of the
thyroid.  It is common, and occurs commonly in the postpartum period.
It should not affect breastfeeding, except if the physician arranges
things so that it does.  The mother should not get a thyroid scan to
make the diagnosis, as this is not necessary.  Any medications she
would take are compatible with breastfeeding.

Jack Newman, MD, FRCPC