Sidebar. Causes of Subclinical Hyperthyroidism (or Low Serum TSH Level).

Origin	Condition
Endogenous
Persistent	Toxic Adenoma
	Toxic Multinodular Goiter
	Graves' disease
	Pituitary disease (Central hypothyroidism) a
Transient	Subacute thyroiditis
	Silent thyroiditis
	Postpartum thyroiditis
	Euthyroid Sick Syndrome
	Initial post-therapy period after treatment for overt hyperthyroidism
Other	Pregnancy (especially during the first trimester)
Exogenous
Iatrogenic	Overtreatment with levothyroxine (most common cause)
	Factitial thyrotoxicosis (surreptitious levothyroxine intake)
	Drug-induced thyroiditis (amiodarone, α-IFN)
	Iodide excess (radiographic contrasts)
	TSH-lowering medications (steroids, dopamine)

^aUsually associated with low Thyroxin and low Triiodothyronine