There are two ways for hyperthyroidism patients to gain weight, one is before drug treatment, and the other is after treatment. One of the characteristics of hyperthyroidism is that the body's metabolism is high, and the synthetic metabolism is relatively lower than the catabolism. Therefore, after suffering from hyperthyroidism, emaciation is a prominent performance, but there are also very few hyperthyroidism patients who not only do not lose weight, but even gain weight. People call this condition "obese hyperthyroidism". This can be seen in children and young women with hyperthyroidism. The formation of obese hyperthyroidism may be because the condition of hyperthyroidism is in the early stage, and the catabolism has not exceeded the anabolism, or it is in the dynamic equilibrium stage of two kinds of metabolism, and the decomposition process and synthesis process in the body are roughly the same. However, when the disease develops further and the consumption exceeds the synthesis, the weight will gradually decrease. After routine treatment, patients with hyperthyroidism gradually get better and gain weight. After a period of treatment, many patients' weight can be restored to the normal level before illness, and many people can exceed the weight level before illness and become fat.

There is also a situation that some hyperthyroidism drugs are hormones at present, and patients will gain weight after taking them for a long time.