A diabetes mellitus patient shows hyperglycemia, glycosuria, polyuria, polydipsia and polyphagia. The root cause of these signs is the deficiency of:

1. Insulin promotes glucose uptake into cells and converts glucose to glycogen, lowering blood sugar. 2. A lack of insulin raises blood sugar (hyperglycemia) and spills glucose into urine (glycosuria). 3. The high urine glucose draws water, causing frequent urination (polyuria), thirst (polydipsia) and hunger (polyphagia). 4. So insulin deficiency is the cause; glucagon excess would not be called a deficiency disorder. 5. Thyroxine and cortiscol shortfalls give other syndromes (myxoedema, shock), not these five signs, so they are ruled out. 6. Therefore insulin deficiency, not any other hormone, links all five clinical signs together. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 16 Plant and Animal Hormones "Diabetes mellitus", p.243_