Which hormone act by crossing cell membrane -
Thyroxine
Insulin
Glucagon
Calcitonin
Ans. A. ThyroxineIntracellular receptors are transcription factors that have binding sites for the hormone (ligand) and for DNA and function as ligand (hormone)-regulated transcription factors.Steroid hormones and the steroid derivative vitamin D3 fulfill this requirement.Thyroid hormones must be actively transpoed into the cell.