Apoptosis is a type of programmed cell death which can be induced by thyroid hormone in pituitary and other cell models. This process is characterized by several biochemical changes, including modifications in plasma membrane lipid composition, mitochondrial membrane dysfunction, and DNA fragmentation, among others. These cellular alterations can be measured using western blotting and flow cytometry techniques. Here we describe the method to detect cleavage of poly-ADP ribose polymerase by western blotting, as well as different flow cytometry-based methods to quantify the sub-G1 hypodiploid cell population, the redistribution of phosphatidylserine to the outer leaflet of plasma membrane, and the loss of the mitochondrial inner membrane potential.