Your  doctor will discover larger lumps in  the thyroid  gland by feeling  your neck during a physical exam. A  doctor may also have you swallow during this exam. 

A diagnosis of goiter may include:

• A hormone test.   A blood  test can show the amount of hormone created by the thyroid and pituitary glands. Thyroid  hormone production will be low for an underactive thyroid gland. The  pituitary gland will try  to stimulate your thyroid gland to produce more hormones by supplying more thyroid-stimulating hormone or TSH.  Goiter that is  associated with an overactive thyroid more than likely  involves a higher level of thyroid hormone in the bloodstream and a lower than normal thyroid stimulating hormone or  TSH level.
• Antibody testing.   The existence  of abnormal antibodies can lead to goiter. This  test can reveal the production of these if they are present. 
• Ultrasonography.   In this exam, a transducer, which looks like a wand, is held over the neck. Sound waves bounce throughout the neck and back which create  images on a computer monitor. Those images will display any enlargement in  the thyroid gland and any  nodules that may be present and  not found during the physical exam. 
• A thyroid scan.   A  thyroid scan involves  a radioactive isotope being injected into the bloodstream - typically through the  vein on the inside part of the elbow. The patient lies on a table with the head stretched backward so that  a camera can take  an image of your thyroid and display it  on a computer monitor. These  scans give us  information regarding the structure and size  of the thyroid. They are more thorough time-consuming  and expensive when compared to  the ultrasound tests.