This document reviews various segmentation methods that have been used to segment thyroid ultrasound images in order to diagnose thyroid diseases. It begins with background on thyroid ultrasound imaging and diseases. It then surveys past studies that have used techniques like thresholding, morphological operations, active contours, and watershed transforms to segment thyroid lobes and nodules. The document applies some of these methods (active contours, morphological operations, watershed) to sample images and compares the results. It concludes that local area based active contours provide the most accurate segmentation of thyroid lobes.