From the Guidelines
Thyroxine (levothyroxine) should be taken first thing in the morning, on an empty stomach, 30-60 minutes before breakfast following a thyroidectomy, with treatment typically beginning immediately after surgery or within the first few days, as recommended by the most recent guidelines 1. The standard starting dose is usually 1.6-1.8 mcg/kg body weight per day, though this may be adjusted based on individual factors such as age and other medical conditions, with consideration for titrating up from a lower starting dose of 25-50 mg in patients older than 70 years and/or frail patients with multiple comorbidities 1. Some key points to consider when taking levothyroxine include:
- Taking the medication consistently at the same time each day to maintain stable hormone levels
- Avoiding calcium supplements, iron supplements, antacids, or certain foods like soy products and high-fiber foods within 4 hours of taking levothyroxine, as these can interfere with absorption
- Regular blood tests (typically every 6-8 weeks initially, then every 6-12 months once stable) to monitor TSH and T4 levels and adjust dosing as needed
- Lifelong replacement therapy is necessary since the thyroid gland has been removed and can no longer produce thyroid hormones naturally, with the goal of preventing symptoms of hypothyroidism and maintaining stable hormone levels 1. It is also important to note that the management of thyroid hormone replacement therapy should be individualized, taking into account the patient's age, medical history, and other factors, with the goal of achieving optimal thyroid hormone levels and preventing complications 1.
From the FDA Drug Label
Levothyroxine Sodium Tablets, USP should be taken in the morning on an empty stomach, at least one-half hour to one hour before any food is eaten
The patient should take levothyroxine (T4) in the morning, on an empty stomach, at least 30 minutes to 1 hour before eating, after thyroidectomy. 2
From the Research
Levothyroxine Replacement Therapy After Thyroidectomy
- The optimal time to start levothyroxine (T4) therapy after thyroidectomy is not explicitly stated in the provided studies, but one study 3 began T4 treatment five days after surgery.
- The initial dose of levothyroxine (L-T4) can be based on the patient's body weight, with a common dose being approximately 1.6 μg/kg/day 4, 5, 6.
- However, the required dose may vary depending on factors such as age, body mass index (BMI), preoperative mean corpuscular volume, and free triiodothyronine (fT3) levels 5.
- Studies have shown that a significant proportion of patients require dose adjustments after starting levothyroxine therapy, with approximately 75% of patients requiring adjustments 4.
- The dose of T4 needed after thyroidectomy can be higher than before surgery, with one study finding that patients required a dose increase of around 30% after surgery 7.
- Different formulas and nomograms have been proposed to calculate the optimal starting dose of levothyroxine, including those based on weight, age, and BMI 5, 6.
- It is essential to monitor thyroid function tests and adjust the levothyroxine dose accordingly to avoid over- or under-substitution 3, 4.