$(a)$ Name the diseases by which a person is likely to suffer due to the deficiency of:
$(i)$ Iodine
$(ii)$ Insulin
$(b)$ How are the timing and amount of hormone secretion regulated in the human system? Explain with an example.

(N/A) $(i)$ Iodine deficiency leads to Goitre.
$(ii)$ Insulin deficiency leads to Diabetes.
$(b)$ The timing and amount of hormone release are regulated by feedback mechanisms.
For example,if the blood sugar level rises,the cells of the pancreas detect this change and respond by secreting more insulin.
As the blood sugar level falls back to the normal range,the secretion of insulin is reduced or inhibited.
This self-regulating system ensures that hormones are secreted only in the required quantity at the appropriate time.