Elevated gamma-glutamyl transferase (ggt) after Levothyroxine in dogs

The FDA has received 43 reports of elevated gamma-glutamyl transferase (ggt) in dogs after Levothyroxine. That is 1.4% of all reports for this medicine, compared with 0.4% across reports for all dog medicines, so it is reported unusually often with this medicine.

43Reports
65%Marked serious
7.0%Recovered
26%Died or euthanised
113 daysTypical onset
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How soon it started

Same day
3 12%
1–2 days
0 0.0%
3–7 days
1 3.8%
1–4 weeks
1 3.8%
Over a month
21 81%

How the animals did

Recovered
2 4.7%
Recovered with lasting effects
1 2.3%
Still unwell when reported
13 30%
Died
2 4.7%
Euthanised
9 21%
Not known
16 37%

Problems reported at the same time

Liver problems
40 93%
Kidney problems
15 35%
Abnormal ultrasound finding
14 33%
Lethargy
13 30%
Loss of appetite
12 28%
Didn't work as expected
11 26%
Death
11 26%
Gall bladder & bile duct disorder
9 21%

Age of the animals

Under 1 year
0
1–3 years
2
4–7 years
3
8–11 years
21
12+ years
17

About this medicine

Levothyroxine treats an underactive thyroid.

Questions owners ask

Can Levothyroxine cause elevated gamma-glutamyl transferase (ggt) in dogs?
43 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 113 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).

Elevated gamma-glutamyl transferase (ggt) with similar medicines

All reported side effects of Levothyroxine in dogs · Medicines most reported with elevated gamma-glutamyl transferase (ggt)