Unusual causes of hyperthyrotropinemia and differential diagnosis of primary hypothyroidism a revised diagnostic flow-chart

AGENDA:

. We describe infrequent conditions of TSH elevation in order to raise awareness of these alternative causes of hyperthyrotropinemia.

. We then propose a flow-chart for the differential diagnosis of PH to reduce the risk of misdiagnosis (Figure 1).

Primary hypothyroidism:

. very common endocrine disease with up to 10-15% of the general population

cause of hyperthyrotropinemia:

. Iodine deficiency

 . Hashimoto’s thyroiditis

. congenital hypothyroidism

. previous surgery/ablative treatments

. Neck radiotherapy

. hypothyroid phase of subacute or silent thyroiditis

. drugs affecting thyroid function ( iodine-rich drugs, cytokines, tyrosine kinases inhibitors, immune checkpoint inhibitors)