Is breast reduction and liposuction safe for hyperthyroid or hypothyroid patients?

Thank you for the question.
Assuming your thyroid hormones are well controlled (with levels checked),  then undergoing breast reduction surgery should not be a problem. To be sure, confirm with your endocrinologist/internist who can communicate with your plastic surgeon.
Once you have done so, I would suggest that you do the following:
1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you're looking for. Ask to see lots of examples of his/her work. 
2. Have a full discussion and communication regarding your desired goals  with your plastic surgeon.  In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as “natural”  or "C or D cup" etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on who makes the bra; therefore, discussing desired cup  size may also be inaccurate. 
 Best wishes.

With a written full medical clearance for surgery from your endocrinologist MD there should be no issues. Understand if not using health insurance for the BR the liposuction in office surgery would be limited to only 1 liter by rule. If in hospital operating room the liposuction rule does not apply.