Which PAS positive component includes the colloid material of thyroid and pars intermedia of the pituitary?

• A. Colloid material of thyroid and pars intermedia of the pituitary
• B. Basement membranes
• C. Glycogen
• D. Fungal walls

Answer: (A)

PAS stains carbohydrate-rich substances, especially glycoproteins and mucopolysaccharides. The colloid in thyroid follicles is thyroglobulin, a large glycoprotein with carbohydrate side chains, so it appears strongly PAS-positive. The colloid-like material in the pituitary’s pars intermedia is also glycoprotein-rich, giving it the same PAS positivity. Therefore, the component that includes both is the colloid material itself. Basment membranes can be PAS-positive due to glycoproteins, and glycogen is PAS-positive but is intracellular, not the colloid material in these glands, so they aren’t the correct match for this context.