Propylthiouracil

證據等級: L5

預測適應症: 6 個

Propylthiouracil: From Hyperthyroidism (Graves’ Disease) to Neonatal Thyrotoxicosis

One-Sentence Summary

Propylthiouracil (PTU) is a thionamide antithyroid agent classically used to control hyperthyroidism, most notably Graves’ disease, and is preferred in pregnancy due to lower placental transfer than methimazole. The TxGNN model predicts relevance for Neonatal Thyrotoxicosis, with 1 clinical trial and 20 publications currently supporting this direction. Evidence is indirect — no dedicated randomized trial exists in neonates for ethical reasons — but it is consistent with established clinical practice of managing maternal Graves’ disease with thionamides to protect the fetus/neonate.

Quick Overview

Item	Content
Original Indication	Not documented in the local regulatory dataset (drug not marketed in Denmark); clinically established for hyperthyroidism/Graves’ disease
Predicted New Indication	Neonatal Thyrotoxicosis
TxGNN Prediction Score	99.40%
Evidence Level	L3
Denmark Market Status	Not Marketed
Number of Marketing Authorisations	0
Recommended Decision	Proceed with Guardrails

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available in the evidence pack. Based on known pharmacology, PTU inhibits thyroid peroxidase, blocking oxidation and organification of iodide and thereby reducing new thyroid hormone synthesis; it also partially inhibits peripheral T4-to-T3 conversion.

Neonatal thyrotoxicosis most commonly arises when maternal TSH-receptor-stimulating antibodies (Graves’ disease) cross the placenta, or less commonly from activating TSHR/GNAS mutations. Because PTU’s mechanism directly suppresses thyroid hormone synthesis, thionamide therapy (PTU or methimazole) is already the clinical standard for managing maternal hyperthyroidism during pregnancy to prevent fetal and neonatal thyrotoxic complications — methimazole is generally preferred postnatally due to PTU’s hepatotoxicity risk, but PTU retains a defined role, particularly in the first trimester. This mechanistic and clinical continuity supports the TxGNN prediction, even though no interventional trial has been conducted directly in thyrotoxic neonates due to obvious ethical constraints.

The same evidence pack also flags two related thyroid-axis conditions — “resistance to thyroid hormone due to a mutation in thyroid hormone receptor beta” (score 99.66%) and “hyperthyroxinemia” (score 99.08%) — but their supporting literature is largely mechanistic/genetic case material rather than treatment evidence, and in one case (PMID 10724359) PTU treatment failed to control the underlying condition. These two are therefore considered lower-confidence signals (internally flagged “Hold”) and are not the focus of this report.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT03066076	Phase 3	Unknown	60	Compares total thyroidectomy vs. thionamide antithyroid drugs in moderate-to-severe Graves’ ophthalmopathy; not a direct neonatal trial, but the thionamide treatment arm provides indirect data on maternal antithyroid therapy relevant to fetal/neonatal thyroid outcomes. Trial status is “Unknown,” indicating possible loss to follow-up.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
33349844	2021	Review/Guideline	J Clin Endocrinol Metab	Guidance on testing, monitoring and treatment of thyroid dysfunction in pregnancy, including antithyroid drug risk-benefit considerations
31345521	2019	Review	Endocrinol Metab Clin North Am	High-risk Graves’ disease in pregnancy treated with PTU in the first trimester, transitioning to methimazole thereafter
25747892	2015	Cohort	Thyroid	Gestational thyrotoxicosis and antithyroid drug use evaluated against neonatal outcomes in an integrated healthcare system
24622372	2013	Review	Lancet Diabetes Endocrinol	Overview of hyperthyroidism in pregnancy; notes adverse outcomes can affect both mother and offspring
32199749	2020	Review/Guideline	Best Pract Res Clin Endocrinol Metab	Management approach to thyrotoxicosis during pregnancy to prevent maternal and fetal complications
6387489	1984	Review	N Engl J Med	Classic review of antithyroid drug pharmacology and mechanism of action
18558604	2008	Case report	Endocr Pract	Persistent neonatal thyrotoxicosis from a rare activating TSHR mutation, illustrating non-autoimmune neonatal disease requiring antithyroid therapy
12201835	2002	Case report	Clin Endocrinol	Neonatal thyrotoxicosis case linked to a maternal TRβ gene mutation (M313T)
596245	1977	Case series	Acta Med Scand	Early description linking postpartum hyperthyroidism exacerbation to neonatal thyrotoxicosis
2090674	1990	Case report	J Endocrinol Invest	Neonatal hepatitis and lymphocyte sensitization following placental transfer of PTU, alongside transient neonatal thyrotoxicosis — relevant to both efficacy and safety monitoring

Denmark Market Information

Propylthiouracil is currently not marketed in Denmark under this evidence pack’s dataset — no marketing authorisations (national Laegemiddelstyrelsen or centralised EMA) were found.

Safety Considerations

Please refer to the approved Summary of Product Characteristics (SmPC) for safety information. No key warnings, contraindications, or drug-interaction data were available in this evidence pack (DDI query: not found). Note as general pharmacological background: PTU as a drug class is associated with recognised hepatotoxicity and agranulocytosis risks, which should be confirmed against the current SmPC before clinical use.

Conclusion and Next Steps

Decision: Proceed with Guardrails

Rationale: Thionamide therapy for maternal Graves’ disease during pregnancy is already established clinical practice, and the available cohort, review, and case-level evidence coherently support PTU’s mechanistic relevance to neonatal thyrotoxicosis prevention/management. However, no dedicated randomized trial in neonates exists (ethically limited), and the drug currently has no marketing authorisation in Denmark.

To proceed, the following is needed:

Danish SmPC warnings/contraindications (DG001, Blocking) — required before any S1 safety assessment
Confirmed mechanism of action data from DrugBank (DG002, High)
Drug interaction data (currently not found)
Regulatory pathway assessment for Danish market entry given current “Not Marketed” status
Pediatric/neonatal dosing and monitoring protocol if pursued clinically
Disclaimer

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