title: Toxicology review and risk assessment of resorcinol: thyroid effects.
abstract: Resorcinol administered at high doses to rodents can disrupt thyroid hormone synthesis and can produce goitrogenic effects. These effects were not seen in a 2-year bioassay at doses of up to 520 mg/kg/day. There are species-specific differences in synthesis, binding, and transport of thyroid hormone that complicate interpretation of goitrogenesis in rodents. Clinical case reports from patients undergoing resorcinol therapy for dermatological indications reveal thyroid side effects when copious amounts of resorcinol-containing ointments are applied to integrity-compromised skin for months to years. Effect levels were greater than 34 mg/kg/day. Occupational epidemiology studies provide no evidence that exposure to resorcinol at levels greater than found in the general environment causes thyroid dysfunction. Studies investigating the relationship between endemic goiter and exposure to "phenolics," including resorcinol, in drinking water do not fulfill accepted scientific criteria for establishing resorcinol as a cause of thyroid disease. Those reports neither quantify exposure levels nor demonstrate dose-response relationships or rule out confounding by the multiple other chemicals present in water supplies, by bacterial contamination of water, or by nutritional factors. A risk assessment comparing potential worst-case exposures to resorcinol through its use in dermatological preparations supports the conclusion that under real-world conditions, human exposures to resorcinol are not expected to cause adverse effects on thyroid function.
authors.affiliation: Cantox Health Sciences International Inc, 2233 Argentia Road, Suite 308, Mississauga, Ontario, Canada L5N 2X7. blynch@cantox.com
authors.forename: Barry S
authors.initials: BS
authors.lastname: Lynch
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Delzell
authors.forename: David H
authors.initials: DH
authors.lastname: Bechtel
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D006727:Hormone Antagonists / Q000009:adverse effects / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D051379:Mice; D016273:Occupational Exposure; D010414:Pennsylvania / Q000453:epidemiology; D051381:Rats; D012118:Resorcinols / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics; D018570:Risk Assessment; D013959:Thyroid Diseases / Q000453:epidemiology / Q000209:etiology*; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018675:Toxicity Tests; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D006727:Hormone Antagonists; D012118:Resorcinols; C031389:resorcinol