Hyperpigmentation of the thyroid has been produced by members of the tetracycline class in the following species: in rats by oxytetracycline, doxycycline, tetracycline PO4, and methacycline; in minipigs by doxycycline, minocycline, tetracycline PO4, and methacycline; in dogs by doxycycline and minocycline; in monkeys by minocycline.
Minocycline, tetracycline PO4, methacycline, doxycycline, tetracycline base, oxytetracycline HCl, and tetracycline HCl were goitrogenic in rats fed a low iodine diet. This goitrogenic effect was accompanied by high radioactive iodine uptake. Administration of minocycline also produced a large goiter with high radioiodine uptake in rats fed a relatively high iodine diet.
Treatment of various animal species with this class of drugs has also resulted in the induction of thyroid hyperplasia in the following: in rats and dogs (minocycline); in chickens (chlortetracycline); and in rats and mice (oxytetracycline). Adrenal gland hyperplasia has been observed in goats and rats treated with oxytetracycline.
Chat online with Pfizer Medical Information regarding your inquiry on a Pfizer medicine.
*Contact Medical Information. 8AM-9PM ET Monday to Friday; excluding holidays.
Submit a medical question for Pfizer prescription products.
To report an adverse event related to the Pfizer-BioNTech COVID-19 Vaccine, and you are
not part of a clinical trial* for this product, click the link below to submit your
*If you are involved in a clinical trial for this product, adverse
events should be reported to your coordinating study site.
If you cannot use the above website, or would like to report an adverse event related
to a different Pfizer product, please call Pfizer Safety at
You may also contact the U.S. Food and Drug Administration (FDA) directly to report
adverse events or product quality concerns either online at