Specialty Spotlights
Endocrinology Calculators Spotlight: TSH, Free T4, HOMA-IR, and Thyroid Nodule Tools
Endocrinology is one of the most calculator-dense specialties in medicine. This spotlight covers six essential tools: TSH/free T4 interpretation, subclinical hypothyroidism management thresholds, TI-RADS thyroid nodule risk scoring, corrected calcium, HOMA-IR, and the FRAX fracture risk tool.
TL;DR: This spotlight covers six essential endocrinology tools: TSH/free T4 interpretation, subclinical hypothyroidism management, TI-RADS thyroid nodule scoring, corrected calcium, HOMA-IR, and FRAX.
Calculator 1: TSH Interpretation Framework
| TSH (mIU/L) | Free T4 | Interpretation |
|---|---|---|
| <0.1 | High | Overt hyperthyroidism |
| <0.1 | Normal | Subclinical hyperthyroidism |
| 0.4–4.0 | Normal | Euthyroid |
| 4.0–10.0 | Normal | Subclinical hypothyroidism |
| >10.0 | Low | Overt hypothyroidism |
| Low | Low | Central hypothyroidism |
Calculator 2: Subclinical Hypothyroidism Thresholds
| TSH Range | Recommendation |
|---|---|
| 4.0–10.0 — Asymptomatic, <70 | Shared decision-making |
| >10.0 — Any age | Treat |
| Any SCH — Pregnancy | Treat |
| SCH — Age >70 with TSH 4–8 | Observe |
Calculator 3: TI-RADS Thyroid Nodule Risk
| Points | TR Level | Malignancy Risk | FNA Threshold |
|---|---|---|---|
| 0 | TR1 — Benign | <1% | No FNA |
| 2 | TR2 — Not suspicious | <2% | No FNA |
| 3 | TR3 — Mildly suspicious | ~5% | FNA if ≥2.5 cm |
| 4–6 | TR4 — Moderately suspicious | ~5–20% | FNA if ≥1.5 cm |
| ≥7 | TR5 — Highly suspicious | >20% | FNA if ≥1.0 cm |
Calculator 4: Corrected Calcium
Corrected Ca = Measured Ca (mg/dL) + 0.8 × [4.0 − Albumin (g/dL)]
Calculator 5: HOMA-IR Quick Reference
Threshold for clinical concern: HOMA-IR >2.5 (general Western populations).
Calculator 6: FRAX for Endocrine Bone Disease
Treat if MOF ≥20% or hip ≥3%.
Evidence
Nair R et al. (2014) demonstrated significant TSH postprandial suppression. Indian J Endocrinol Metab. 2014;18(5):705–707. PMID: 25285290.
Boronat M (2020) illustrated central hypothyroidism diagnostic pitfall. Endocrinol Diabetes Metab Case Rep. 2020. PMID: 32698125.
References
- Nair R, et al. Indian J Endocrinol Metab. 2014;18(5):705–707. PMID: 25285290.
- Boronat M. Endocrinol Diabetes Metab Case Rep. 2020. PMID: 32698125.
- Stott DJ, et al. (TRUST trial) N Engl J Med. 2017;376(26):2534–2544. PMID: 28402245.
- Tessler FN, et al. J Am Coll Radiol. 2017;14(5):587–595. PMID: 28372962.
Related calculators
- Corrected Calcium Calculator - Nephrology