Propylthiouracil

證據等級: L5

預測適應症: 3 個

Propylthiouracil: From Hyperthyroidism to Thyroid Hormone Resistance (THRB Mutation)

One-Sentence Summary

Propylthiouracil (PTU) is a thionamide-class antithyroid drug historically used to manage hyperthyroidism, including Graves' disease. TxGNN predicts a possible link to resistance to thyroid hormone due to a mutation in thyroid hormone receptor beta (RTH-β), but this is currently supported only by 0 clinical trials and 6 case-report/mechanistic publications — evidence is preliminary at best.

Quick Overview

Item	Content
Original Indication	Not available from New Zealand regulatory data (no licenses on record); based on established pharmacology, PTU is used for hyperthyroidism (e.g., Graves' disease)
Predicted New Indication	Resistance to thyroid hormone due to a mutation in thyroid hormone receptor beta
TxGNN Prediction Score	99.66% (global rank 3394)
Evidence Level	L4
New Zealand Market Status	Not marketed
Number of Authorizations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available in this evidence pack. Based on known pharmacology, propylthiouracil is a thionamide that inhibits thyroid peroxidase, blocking new thyroid hormone synthesis and also reducing peripheral conversion of T4 to T3 — its efficacy in hyperthyroidism (notably Graves' disease) is well established.

Resistance to thyroid hormone (RTH-β) is superficially related because it shares the same hormone axis and can present with biochemical findings that mimic hyperthyroidism (elevated T4/T3), sometimes leading to misdiagnosis. This overlap likely explains why TxGNN links the two conditions.

However, the mechanistic fit is questionable: RTH-β is caused by reduced receptor responsiveness to thyroid hormone, not excess hormone production. PTU works upstream by suppressing synthesis, so it does not correct the underlying receptor defect. Consistent with this, several of the literature items below describe RTH patients who were misdiagnosed as thyrotoxic and treated with PTU without clinical benefit (e.g., worsening goiter). This should be treated as a caution flag rather than confirmatory evidence.

Clinical Trial Evidence

Currently no related clinical trials registered.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
10724359	1999	Case report	Endocrine Journal	Thai woman with de novo L330S THRB mutation; previously treated with propylthiouracil for presumed thyrotoxicosis, with goiter enlarging rather than improving — illustrates misdiagnosis risk and lack of PTU benefit in RTH
12201835	2002	Case report	Clinical Endocrinology	Two RTH cases (M313T mutation) in one family, including neonatal thyrotoxicosis; discusses diagnostic overlap with true thyrotoxicosis
18561095	2009	Case report	Exp Clin Endocrinol Diabetes	Turkish family with P453A THRB mutation causing RTH; describes clinical/biochemical presentation
14684607	2004	Preclinical (animal)	Endocrinology	Mouse model study of dominant-negative TR-β mutation (Δ337T) and its cardiac effects in RTH
21909131	2012	Preclinical (animal)	Oncogene	Thrb(PV/PV) mouse model shows thyroid hormone activates tumor cell proliferation via mutant TR-β, linking RTH mutation to follicular thyroid carcinoma
22919057	2012	Preclinical (animal)	Endocrinology	Role of TSH in spontaneous thyroid carcinoma development in mice with heterozygous THRB mutation

New Zealand Market Information

Propylthiouracil is not currently authorized for marketing in New Zealand (0 licenses on record in this evidence pack).

Safety Considerations

Please refer to the package insert for safety information.

(Note: TFDA label warnings/contraindications and drug interaction data are marked as a Blocking data gap in this evidence pack — see Conclusion.)

Conclusion and Next Steps

Decision: Hold

Rationale: Evidence for this indication is limited to case reports and preclinical/animal mechanism studies (no clinical trials, no observational cohorts), and several of the case reports actually document PTU being ineffective when misapplied to RTH patients — mechanistically, PTU suppresses hormone synthesis but does not address the receptor-level defect that defines RTH. Combined with a Blocking data gap on safety labeling, the evidence does not support advancing this candidate at this time.

To proceed, the following is needed:

TFDA/regulatory package insert data (warnings, contraindications) — currently a Blocking gap
Confirmed mechanism of action (DrugBank MOA) to properly assess mechanistic plausibility for RTH-β
Expert endocrinology review reconciling why a synthesis inhibitor would benefit a receptor-resistance disorder
If pursued, a defined regulatory pathway for New Zealand market entry (currently unmarketed, 0 licenses)
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.