From the FDA Drug Label
Adverse reactions associated with levothyroxine sodium therapy are primarily those of hyperthyroidism due to therapeutic overdosage They include the following: • General:fatigue, increased appetite, weight loss, heat intolerance, fever, excessive sweating • Central nervous system:headache, hyperactivity, nervousness, anxiety, irritability, emotional lability, insomnia • Musculoskeletal:tremors, muscle weakness, muscle spasm • Cardiovascular:palpitations, tachycardia, arrhythmias, increased pulse and blood pressure, heart failure, angina, myocardial infarction, cardiac arrest • Respiratory:dyspnea • Gastrointestinal:diarrhea, vomiting, abdominal cramps, elevations in liver function tests • Dermatologic:hair loss, flushing, rash • Endocrine:decreased bone mineral density • Reproductive:menstrual irregularities, impaired fertility
Hot flashes are not explicitly listed as an adverse reaction. However, heat intolerance is mentioned, which could be related to hot flashes. Considering the information provided, it is possible that thyroid medication could cause symptoms similar to hot flashes in a severely hypothyroid post-menopausal woman, but this is not directly stated in the drug label 1.
From the Research
Thyroid medication can cause hot flashes in a severely hypothyroid post-menopausal woman, particularly when starting treatment or adjusting dosages, as evidenced by the most recent study 2 which highlights the importance of proper dosing and monitoring of thyroid stimulating hormone (TSH) levels. When initiating treatment, levothyroxine (Synthroid, Levoxyl) or other thyroid medications restore normal metabolism, which can temporarily disrupt temperature regulation as the body adjusts. If a dose is too high, it may cause hyperthyroid symptoms including hot flashes, sweating, heart palpitations, and anxiety. Some key points to consider:
- The standard approach is to start with a low dose (usually 25-50 mcg daily for older adults or those with heart conditions) and gradually increase every 4-6 weeks based on thyroid function tests until reaching the appropriate maintenance dose, as suggested by 3.
- If hot flashes are severe or persistent, the medication dose may need adjustment, and it's essential to distinguish these medication-related hot flashes from menopausal hot flashes, which can occur simultaneously and complicate the clinical picture.
- Regular monitoring of TSH levels is crucial to ensure proper dosing, and modifying treatment to a particular TSH target or adjusting based on a low T3 level does not seem to enhance patient outcomes, as noted in 2.
- The use of levothyroxine monotherapy is still the recommended treatment for hypothyroidism, and combined therapy with liothyronine should be considered on a case-by-case basis, as discussed in 4.