Extracellular receptors must be required for the action of:
I. Oxytocin
II. Thyroxine
I. Epinephrine
IV. Glucagon
l, ll, lll & IV
I. IV only
I, Ill, IV
III & IV only
Extracellular receptors are required for the action of three out of the four given hormones. These hormones are Oxytocin, Epinephrine and Glucagon. Extracellular receptors are not required for the action of Thyroxine. Thyroxine is a thyroid hormone that interacts with intracellular receptors, rather than membrane-bound receptors. Hence, the correct answer is option 3.