Mary-Margaret:  This mother's hyperthyroidism is essentially a
hypermetabolic state, i.e. her metabolic rate is increased.  To improve
her nutritional status she needs to take in an increased number of
calories (a consult with a dietitian may help her to work out her
increased caloric needs).  As we know, lactation also requires some extra
calories, so she needs to include that in her calculation.  I am not
aware of any problem with decreased milk supply as long as she stays well
hydrated and takes in the requisite number of calories.  As for the
weight loss, I imagine that weaning would only conserve the 200-500
calories/day that lactation consumes, but that only prevents a loss of
1/2 to 1 lb/week.  In hyperthyroidism, the weight loss can be
considerably more, and if she continued to breastfeed, she could prevent
that extra 1/2 to 1 lb/week by eating an extra 200-500 calories/day
anyway.  Her nutritional needs will change as the PTU starts to work, so
she needs to adjust her diet accordingly with the help of a dietitian.
She needs also to be monitored regularly by a physician to ensure that
her symptoms are not due to complications of her hyperthyroidism, such as
heart failure.  Hope this helps.  Alicia.  [log in to unmask]