Complications
Adrenal crisis may occur if levothyroxine therapy is initiated in the setting of untreated adrenal insufficiency. Patients with adrenal crisis present with nausea, vomiting, dizziness due to hypotension, and possible loss of consciousness.
Adrenal insufficiency should be treated with glucocorticoids prior to the start of thyroxine replacement. If it is not feasible to assess adrenal function prior to initiating thyroxine replacement, prophylactic treatment with steroids should be considered.[1]
Chronic over-replacement of thyroid hormone may induce osteoporosis, particularly in post-menopausal women.[48] However, debate stills exists regarding this association. A literature review found that only 9 of 31 studies showed consistently adverse effects on bone mineral density with use of physiological and/or supraphysiological thyroid hormone therapy.[64]
Patients, and particularly peri-menopausal women, should follow the general advice of the primary care provider regarding screening for osteoporosis.
Myxoedema coma is a rare life-threatening state in which severe hypothyroidism markedly worsens.
In general, it occurs in older people and is usually precipitated by an underlying medical illness.[62] The mortality rate associated with myxoedema coma is 25% to 60%.[63]
Clinical features include hypothermia, change in mental status, hypotension, bradycardia, hypoventilation, and diffuse non-pitting oedema.[63]
Patients with myxoedema coma should be treated in the intensive care unit under the supervision of an endocrinologist.
Thyrotoxicosis can occur from overdose of levothyroxine.
An appropriate management strategy includes discontinuation for several days, followed by resumption of replacement therapy at a lower dose.
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