$(a)$ Name the hormone which is injected to a diabetic patient.
$(b)$ Why should we use iodised salt in our diet?
$(c)$ If iodine is insufficient in one's diet,what might be the deficiency disease and its symptoms?

(A) The hormone injected into a diabetic patient is $Insulin$.
$(b)$ We should use iodised salt in our diet because iodine is essential for the thyroid gland to synthesize and secrete the hormone $Thyroxine$. $Thyroxine$ plays a crucial role in regulating the metabolism of carbohydrates,proteins,and fats in the body,ensuring a balanced growth and development.
$(c)$ If iodine is insufficient in one's diet,it leads to a deficiency disease known as $Goitre$. The primary symptom of $Goitre$ is a swollen neck,caused by the enlargement of the thyroid gland as it attempts to produce more $Thyroxine$ in response to low iodine levels.