Cynthia:

        The test for a hyperactive thyroid is a Thyroid Panel which contains
3 tests of thyroid function.  This test just involves taking a blood
specimen and is certainly not dangerous.   Other kinds of scans can be done,
but generally do not require removal of the infant for long periods.

        If the mom is suffering from severe hyperthyroidism,  then she has
several choices:

        1)      Take Propylthiouracil to suppress T4 production.  This
product is safe in a breastfeeding mom  if her infants' thyroid function is
occassionally checked.

         2) Ablation(destruction) of the thyroid gland with radioactive
I-131.   Radioactive iodine is so dangerous to a Breastfeeding infant,  that
they MUST be removed.   The rate of decay(radioactive and biologic) is
controversial,  but easily extends over many weeks to months.  If she
chooses the radioactive technique,  I personally believe it is safer for the
infant to be removed permanently from the breast.

TWHale