Final answer:
The symptoms presented are indicative of hyperthyroidism, a condition characterized by an overactive thyroid gland, leading to an increased metabolic rate and associated symptoms such as weight loss and tachycardia.
Step-by-step explanation:
The collection of symptoms including sudden weight loss, anxiety, tremor, sweating, fine brittle hair, increased appetite, and tachycardia (increased heart rate) suggests the disorder in question is hyperthyroidism.
Hyperthyroidism is a condition where the thyroid gland is overactive and produces too much thyroid hormone, leading to an accelerated metabolic rate. This can manifest in symptoms like rapid weight loss despite an increased appetite, sweating, fine or brittle hair, anxiety, and a faster heartbeat. In contrast, hypothyroidism, another thyroid disorder, generally causes symptoms such as weight gain, cold sensitivity, and reduced mental activity due to an underactive thyroid gland.