 [ Symptoms ] i have been ill for a while and lost quite a bit of muscle and weight suggestions on getting it back and why i hurt  so i have a thyroid disorder and i had it tested a month ago and still no answer back from anyone i am feeling a bit better now but i can not seem to gain back the weight or the muscle specifically on my legs and they hurt quite frequently my legs were the strongest part before i got sick and they still are pretty strong but i have never had leg pain when i ran or carried things before and it worries me how thin they are now along with the pain should i be concerned suggestions [ Disease ] well individuals with low igg levels tend to get infection more frequently as igg antibodies are responsible for preventing infection in the body so in case of igg deficiency the body tend to get frequent infection so you should consult an immunologist and get evaluated and igg replacement therapy can help in reducing the frequency of infection in case if you get infection you should immediately get a proper treatment to avoid worsening hope this helps regards