Reaction profile

The FDA adverse-event record for low thyroxine (t4)

586 FDA adverse-event reports reference low thyroxine (t4) (VeDDRA 2670). See the species, breeds, and drugs most associated with it below.

586
reports citing this reaction
17.2%
death-coded share
Dog
most-affected species
Trilostane
most-associated drug
Verify with FDA CVM →
586
Total Reports
101
Deaths
17.2%
Death Rate

Species Most Affected

Dog 522
Cat 64

Breeds Most Affected

Retriever - Labrador 62
Domestic Shorthair 51
Retriever - Golden 37
Crossbred Canine/dog 35
Shepherd Dog - German 23
Chihuahua 17
Boxer (German Boxer) 17
Maltese 14
Beagle 14
Terrier - Yorkshire 13

Associated Drugs

Trilostane 160
Bedinvetmab 70
Levothyroxine Sodium 53
Carprofen 45
Maropitant Citrate 45
Oclacitinib Maleate 44
Gabapentin 36
Prednisone 33
Thiamazole 32
Afoxolaner 31
Milbemycin Oxime + Spinosad 30
Fluralaner 13.64% 12-Week Chew 24
Pyrantel Pamoate;Sarolaner 24
Levothyroxine 20
Moxidectin 17
Metronidazole 17
Fluralaner Chew Tablets 16
Grapiprant 15
Anti-Il31 Mab Mcs Lot #1283563 15
Doxycycline 14

Low thyroxine (T4) Reaction Insights

586 reports name Low thyroxine (T4); 101 recorded a death outcome (17.2% of reported events, not a population-level mortality rate). VeDDRA code: 2670.

By species: Dog (522 reports), Cat (64 reports). By breed: Retriever - Labrador (62), Domestic Shorthair (51), Retriever - Golden (37).

Most co-reported drugs: Trilostane (160 reports), Bedinvetmab (70 reports), Levothyroxine Sodium (53 reports), Carprofen (45 reports).

Read these counts as reporting volume, not risk: per our methodology, co-reporting reflects temporal association captured in voluntary submissions, not proof that a drug caused this reaction. A widely-prescribed drug will rack up more raw co-reports at an identical true rate than a rarely-used one, so compare within similar-exposure products.

Source: FDA Center for Veterinary Medicine openFDA Animal & Veterinary Adverse Events (CVM AER) · 2025

Every figure on PlainBreed is rendered directly from FDA openFDA adverse event data, no number is typed in by an editor. This page draws directly on FDA openFDA data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.