Complications

Complication
Timeframe
Likelihood
short term
low

May occur with a high initial dose of levothyroxine in patients with coronary artery disease.

long term
low

Most likely due to nonadherence, and less often from drug interactions and coexisting illness.

long term
low

May occur with overtreatment.

Acute atrial fibrillation

long term
low

May occur with overtreatment.

Osteoporosis

long term
low

Myxedema 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. The mortality rate associated with myxedema coma is 25% to 60%.[3][57]

Clinical features include hypothermia, change in mental status, hypotension, bradycardia, hypoventilation, and diffuse nonpitting edema.[1][3][57]

Patients with myxedema coma should be treated in an intensive care setting under the supervision of an endocrinologist.

variable
medium

Subclinical hypothyroidism or the presence of thyroid antibodies has been found to be associated with an increased risk of complications in pregnancy, such as preeclampsia, perinatal mortality, recurrent miscarriage, and fetal neurologic maldevelopment.[53]​ There is no good evidence that treatment of subclinical hypothyroidism during pregnancy reduces the incidence of these complications.[43][56]​ However, some experts recommend treating this condition in pregnancy.[30][47]

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