Figured another update was in order. Sadly Hilda is not doing well, but is still with us. After her thyroid result she got started on thyroid meds (methrimazole) last Tuesday (March 25). Originally it was 0.2mL twice a day but after I reported her having a lack of appetite and lethargy and more weight loss they reduced it to 0.1mL twice a day instead. Prior to that she kept losing weight and has continued to lose weight on the meds. It's tough because before the meds at least she was active and eating a lot despite losing weight and having an up and down fever.
Now since the meds she seems a lot more like she's ailing-- spends a lot of time lying around and appetite is way down. I am assisting where I can with her getting food in. She is still eating some on her own as well. The vet said it could just take time for her hormones to balance but I'm not as optimistic as them. Her weight is down to 560g and I notice her sometimes stumbling over a back leg walking (this actually started a few weeks ago but got more noticeable). Definitely worried that she is entering that zone where she won't be able to turn things around but we'll see.
HUGS
Thyroid medication is unfortunately not easy to get right and stable with guinea pigs although it has generally improved in recent years. Treatment of metabolic issues and organs in guinea pigs is still a rather new area in guinea pigs. All you and your vet can is try your best. It is one of these things where you are still a bit between a rock and a hard place in terms of treatment.
Fingers firmly crossed for your old lady!
Looking After Guinea Pigs With Limited or No Mobility