Hypoadrenocorticism after Levothyroxine in dogs

23 reports to the FDA describe hypoadrenocorticism in dogs given Levothyroxine. That is 0.8% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported unusually often with this medicine.

23Reports

78%Marked serious

4.3%Recovered

8.7%Died or euthanised

120 daysTypical onset

How soon it started

Same day

1 6.3%

1–2 days

0 0.0%

3–7 days

0 0.0%

1–4 weeks

0 0.0%

Over a month

15 94%

How the animals did

Recovered

1 4.3%

Still unwell when reported

9 39%

Euthanised

2 8.7%

Not known

11 48%

Problems reported at the same time

Abnormal adrenocorticotropic hormone (acth) stimulation test

17 74%

12 52%

8 35%

7 30%

6 26%

6 26%

5 22%

5 22%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Levothyroxine treats an underactive thyroid.

Questions owners ask

Can Levothyroxine cause hypoadrenocorticism in dogs?: 23 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
How soon after a dose was it reported?: In half of the reports with dates, it started within 120 days of the first dose.
What should I do?: Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Hypoadrenocorticism with similar medicines

Hypoadrenocorticism after Trilostane (Vetoryl) 689 reports · 5.8% of its reports
Hypoadrenocorticism after Insulin 21 reports · 0.3% of its reports

All reported side effects of Levothyroxine in dogs · Medicines most reported with hypoadrenocorticism