Hypothyroidism

• Diagnosis: increased TSH with decreased free T4.
• Additional tests: anti-thyroid peroxidase (anti-TPO) antibodies to differentiate with Hashimoto hypothyroidism.
• Symptoms
  • Fatigue, difficulty concentrating, weakness,...
  • Cold intolerance (always feeling cold).
  • Constipation.
  • Dry skin.
• Therapy
  • If there is another indication, such as a persistent risk of cardiac arrhythmias, amiodarone is continued as normal. Whether or not to stop amiodarone should be decided by the treating cardiologist.
  • Replacement with thyroid hormone (T4), this should only be started if TSH > 10 mU/l.
    Goal: aim for a TSH of 1-4 mU/l. Avoid oversubstitution with a suppressed TSH.
  • After discontinuation of amiodarone, hypothyroidism can disappear again and thyroid hormone replacement can often also be reduced and stopped.

Hyperthyroidism

• Diagnosis : very low TSH with increase in both free T3 and free T4.
• Additional tests : ultrasound and Doppler of the thyroid gland to distinguish between type 1 and type 2 amiodarone-induced hyperthyroidism (AIT).
  • Type 1 (due to an excess of iodine): high vascularization of the thyroid gland on ultrasound.
  • Type 2 (amiodarone-induced destructive thyroiditis due to direct toxicity): low to no vascularization of the thyroid gland on ultrasound.
  • There are often mixed forms and the distinction between the two types is not clear.
• Symptoms : 
  • Unexplained weight loss, fatigue, weakness,...
  • Heat intolerance (always feeling warm), sweating.
  • Nervousness, anxiety.
  • Palpitations, increase in cardiac arrhythmias (AF, VT,...).
  • Diarrhea.

• Therapy :
  • Amiodarone is usually stopped unless there is a compelling indication to continue taking it. Whether or not to stop amiodarone should be decided by the treating cardiologist.
  • Treatment is best done in collaboration with an endocrinologist.
  • Thiamazol (Strumazol - dose: 30 mg per day, in severe cases up to a maximum of 60-90 mg per day). Objective: inhibition of new production of thyroid hormone.
  • If there are arguments for type II AIT: association of glucocorticosteroids, for example prednisone: start with 30 mg/day. Reduce dose over 2-3 months. Objective: inhibition of thyroid inflammation with a decrease in the release of thyroid hormone from the thyroid gland.
  • In case of insufficient effect of standard therapy or in severe cases requiring faster recovery of euthyroidism, sodium perchlorate may be associated (dosage: 2x 500 mg per day). Objective: inhibition of iodine uptake in the thyroid gland, thereby inhibiting new production of thyroid hormone.
  • Sometimes, propranolol is associated in the acute phase to slow down the conversion of T4 to T3. When treating HFrEF, this is best not done and maintenance therapy with the evidence-based beta blocker is best continued (bisoprolol, carvedilol, metoprolol succinate or nebivolol). With a faster heart rhythm, the dose is best increased if possible.
  • In case of persistent hyperthyroidism resistant to drug therapy or if continued amiodarone is necessary from a cardiac point of view, a total thyroidectomy can be considered.