Complete the following analogy-based questions:
$1$. Juxtaglomerular cells of kidney : Erythropoietin :: Atrial wall of heart : .....
$2$. Follicle : Estrogen :: Corpus luteum : .....
$3$. Decrease in glucose utilization at cellular level : Hyperglycemia :: Decrease in blood glucose level : .....
$4$. $\alpha$-cells of pancreas : Glucagon :: $\beta$-cells of pancreas : .....

(A-D) $1$. The atrial wall of the heart secretes Atrial Natriuretic Factor $(ANF)$ in response to increased blood pressure.
$2$. The ovarian follicle secretes estrogen,while the corpus luteum primarily secretes progesterone.
$3$. $A$ decrease in cellular glucose utilization leads to hyperglycemia (high blood sugar),whereas a decrease in blood glucose levels is known as hypoglycemia.
$4$. The $\alpha$-cells of the pancreas secrete glucagon,while the $\beta$-cells of the pancreas secrete insulin.