Hyperthyroidism is the medical term for an overactive thyroid, a special type of thyrotoxicosis.
It can be classified either as a primary hyperthyroidism (the proper thyroid hyperfunction) or as a secondary hyperthyroidism (an excessive stimulus caused by hypersecrection of TSH, which can be produced by tumors of the pituitary gland for example)
The term cachexia refers to a pathological loss of weight.
Cachexia does not only mean a full reduction of body fat. It includes a general atrophy with a gradual loss of function of the organs.
Most notably the reduction of fat and muscle proteins can be observed.