How does the shape of a Thyroid epithelial cell help it do it's job

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All epithelial cells have specific functions. Squamous cells are good barriers against acids, columnar and cubiodal are good secretors. Thyroid follicles are lined by cuboidal cells that are able to secrete colloid fluid where the thyroid hormones are produced. Being rounder than squamous allows for permeation of thyroglobulin-iodine complex and allows for iodine transfer to the center to produce thyroxine and triiodothyronine, which can then be secreted back out of the cuboidal cell and enter blood circulation.