What are the leading causes of decreased thyroid uptake?

Subacute thyroiditis: Inhomogeneous,decreased uptake in a mildly enlarged gland; patients report a painful, swollen gland.
Multinodular goiter: Inhomogeneous, enlarged gland with focal areas of increased and decreased uptake; diagnosis may be confirmed by thyroid scan.
Thyroid-blocking medication: These include propylthiouracil and a recent iodine load (e.g., intravenous iodinated contrast material from CT, IVP).
Exogenous thyroid hormone administration Primary hypothyroidism