What is the appropriate next dose increase for a patient currently taking 135 mg of NP Thyroid (desiccated thyroid extract)?

Dose Increase for NP Thyroid from 135 mg

Increase the dose to 150 mg of NP Thyroid (an increment of 15 mg), and recheck TSH and free T4 levels in 4-8 weeks. 1

Dosing Algorithm

The FDA-approved NP Thyroid label explicitly states that increments of 15 mg every 2 to 3 weeks are the standard approach for dose adjustments 1. Since your patient is currently on 135 mg, the next logical dose is 150 mg.

Key Considerations for This Adjustment:

Timing of reassessment:

• Check TSH and free T4 levels 4-8 weeks after the dose change 2, 1
• Do not adjust sooner, as TSH levels need adequate time to plateau, particularly with smaller dose increments 2

Target range:

• Aim for TSH in the normal reference range (typically 0.5-4.5 mIU/L, though some advocate for 1-2 mIU/L) 2
• If the patient remains symptomatic despite TSH in the upper half of normal range, consider targeting the lower half of the reference range 3

Maintenance expectations:

• Most patients require 60-120 mg/day of desiccated thyroid for maintenance 1
• Your patient at 135 mg is slightly above this typical range, which may indicate:
  • Reduced thyroid reserve
  • Malabsorption issues
  • Non-compliance (though less likely if TSH remains elevated)
  • Interference from medications or supplements

Important Caveats

Age and cardiac considerations:

• If the patient is >50-60 years old or has cardiovascular disease, proceed cautiously with dose increases 2
• Monitor for anginal symptoms, which would necessitate dose reduction 1

Doses above 180 mg:

• The FDA label states that failure to respond to 180 mg suggests lack of compliance or malabsorption 1
• If your patient eventually requires doses approaching or exceeding 180 mg, investigate:
  • Medication adherence
  • Timing of administration (should be 30-60 minutes before breakfast on empty stomach) 2
  • Interfering substances (calcium, iron, PPIs, soy, fiber) 2
  • Gastrointestinal disorders affecting absorption 4

Desiccated thyroid considerations:

• NP Thyroid contains a 4:1 ratio of T4:T3 by weight 2
• This produces higher T3 levels than levothyroxine monotherapy, which can occasionally cause symptoms of mild hyperthyroidism even when TSH is normal 5
• The T4 levels may appear misleadingly low on labs while T3 is elevated 5

Biotin interference:

• Ensure the patient stops any biotin supplementation at least 2 days before thyroid function testing, as it interferes with immunoassays 1

Monitoring Plan

After increasing to 150 mg:

1. Recheck TSH and free T4 in 4-8 weeks 2, 1
2. Make further 12.5-15 mg adjustments as needed based on results 2, 1
3. Once stable, monitor TSH every 6-12 months 2

The 15 mg increment is conservative, evidence-based per the FDA label, and minimizes risk of overshooting into hyperthyroidism while systematically approaching the therapeutic target.