@beetle00 I have a friend who also have hyperthyroidism, dependent of her husband who was granted with visa 189, she is now in Melbourne. Medical staff of St. Lukes just required her to share her record to them and asked a clearance from her Dr. Just that, she wasn't required to undergo operation, was only given prescription maintenance. And according to their agent, there is a certain limit in the amount of maintenance to consider.
I suggest you consult another dr. and yes an agent to get advise for your case as what @batman suggested.