Final answer:
The symptoms suggest either diabetes mellitus or diabetes insipidus, both of which involve fluid imbalances and dehydration, with diabetes insipidus specifically involving a deficiency of antidiuretic hormone (ADH).
Step-by-step explanation:
The symptoms described in the question are indicative of a condition that disrupts the normal balance and retention of fluids in the body. Two possibilities for these symptoms are diabetes mellitus and diabetes insipidus. Diabetes mellitus is characterized by excessive urination (polyuria), excessive thirst (polydipsia), and excessive hunger (polyphagia), all due to high levels of glucose in the bloodstream, which the kidneys attempt to filter. Insulin deficiency or resistance prevents cells from absorbing glucose effectively, leading to cell starvation. Conversely, diabetes insipidus involves chronic underproduction of antidiuretic hormone (ADH) or a mutation in the ADH receptor, leading to an inability to retain water, which results in dehydration and a constant need to drink water. The low specific gravity of the urine suggests the kidneys are not concentrating urine properly, which might be due to the lack of ADH's effects on the kidneys. Dehydration is a significant concern in both conditions and is characterized by symptoms such as dry mouth, dizziness, fatigue, and low urine output.