What is the equivalent dose of levothyroxine (T4) for NP Thyroid (thyroid extract) 90 mg?

From the Guidelines

To convert from NP Thyroid 90 mg to levothyroxine (T4), the equivalent dose would be approximately 75-88 mcg of levothyroxine. When switching from desiccated thyroid products like NP Thyroid to synthetic levothyroxine, it's essential to consider that NP Thyroid contains both T3 (liothyronine) and T4 (levothyroxine) hormones, while levothyroxine contains only T4. NP Thyroid 90 mg contains approximately 38 mcg of T4 and 9 mcg of T3. Since T3 is more potent than T4, the T3 component needs to be accounted for in the conversion. The T3 in NP Thyroid (9 mcg) is roughly equivalent to an additional 37-50 mcg of T4.

Key Considerations for Conversion

• The conversion should always be done under medical supervision, as thyroid hormone replacement requires careful monitoring 1.
• After switching medications, thyroid function tests should be performed after 6-8 weeks to ensure proper dosing, as individual responses vary.
• Symptoms should be monitored during the transition, and dose adjustments may be necessary.
• It is crucial to evaluate TSH levels, with the option of also including FT4, to monitor for asymptomatic patients on therapy, as recommended in the management of immune-related adverse events in patients treated with immune checkpoint inhibitor therapy 1.

Monitoring and Adjustment

• TSH and FT4 should be used for case detection in symptomatic patients, and low TSH with a low FT4 is consistent with central hypothyroidism, which requires further evaluation 1.
• For patients with moderate symptoms, able to perform activities of daily living (ADL), and TSH persistently above 10 mIU/L, consideration should be given to holding immune checkpoint inhibitor therapy until symptoms resolve to baseline, and prescribing thyroid hormone supplementation 1.

From the Research

Equivalent Dose of Levothyroxine (T4) for NP Thyroid (Thyroid Extract) 90 mg

There are no research papers provided that directly address the equivalent dose of levothyroxine (T4) for NP Thyroid (thyroid extract) 90 mg.

Available Information on Levothyroxine and Thyroid Extract

• The provided studies discuss the treatment of hypothyroidism with levothyroxine (T4) and the use of desiccated thyroid extract (DTE) as a form of combination therapy 2.
• DTE is a form of combination therapy in which the LT4/LT3 ratio is approximately 4:1, with the mean daily dose of DTE needed to normalize serum TSH containing approximately 11 mcg T3 2.
• However, the studies do not provide a direct conversion or equivalent dose of levothyroxine for NP Thyroid (thyroid extract) 90 mg.

Considerations for Levothyroxine Dosing

• Initial dosing of levothyroxine can vary greatly and may be based on the amount of residual thyroid function retained by the patient, the body weight or lean body mass of the patient, and thyroid-stimulating hormone levels 3.
• Dose adjustments may need to be made in patients with concomitant medical conditions, in patients taking certain medications, as well as in elderly patients 3.
• Patients who have undergone any weight or hormonal changes may require dose adjustments, and the majority of pregnant women require increased doses of levothyroxine 3.

Key Points

• The provided studies do not directly address the equivalent dose of levothyroxine for NP Thyroid (thyroid extract) 90 mg.
• Levothyroxine dosing can vary greatly and may require adjustments based on individual patient factors 3.
• Desiccated thyroid extract (DTE) is a form of combination therapy with a LT4/LT3 ratio of approximately 4:1, but the studies do not provide a direct conversion to levothyroxine for NP Thyroid (thyroid extract) 90 mg 2.