Question

diabetes insipidus is caused by:
a excessive antidiuretic hormone.
b insufficient antidiuretic hormone.
c excessive thyroid hormone.
d insufficient thyroid hormone.

Explanation:

Diabetes insipidus is a disorder where the body fails to regulate water properly. Antidiuretic hormone (ADH) is responsible for controlling the amount of water reabsorbed by the kidneys. When there is insufficient ADH (either due to problems in the hypothalamus - which produces ADH, or the pituitary gland - which releases it), the kidneys cannot reabsorb water effectively. This leads to excessive urination (polyuria) and increased thirst (polydipsia), which are characteristic symptoms of diabetes insipidus. Excessive ADH would lead to water retention (not the case in diabetes insipidus). Thyroid hormone is involved in metabolism (e.g., regulating energy production, growth, and development), and its excess or deficiency causes conditions like hyperthyroidism (e.g., Graves' disease) or hypothyroidism (e.g., Hashimoto's thyroiditis) respectively, not diabetes insipidus.

Answer:

B. Insufficient antidiuretic hormone.