Hello, Your sister may suffer from hyperthyroidism which occurs when thyroid gland produces too much of the hormone called thyroxine. In most people with hyperthyroidism occurs thyroid enlargement which you may see as a swelling in the front site of the neck. Other symptoms include: sudden weight loss even when appetite is the same or even increase, anxiety, nervousness, troubles with sleeping, rapid heart beat, diarrhea, thinning hair/ hair loss, sweating, heat intolerance. Hyperthyroidism is diagnosed by: -blood tests - TSH level and thyroid hormone levels (T4,T3) -thyroid ultrasound. In my opinion you should contact your doctor so that he or she can examine your sister to check her thyroid. Hope I have answered your question. If you have any further questions I will be happy to help.