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[Natiimy]

Hello,

I would like to ask for a veterinary opinion regarding my dog Scooby.

Scooby is a Chihuahua, male, almost 8 years old, weighing about 6 kg (13.2 lbs). Overall, he appears to be in good condition. He has a normal appetite, wants to go for walks, is interested in his surroundings, and still wants to play. His coat and skin look normal, with no dermatological issues.

However, I noticed that he has lost some weight compared to before and seems to get tired more quickly after intense activity. For example, he may run actively for a few minutes but then prefers to rest. At the same time, he is not lethargic — he is alert, engaged, and behaves normally for his age.

About 3 months ago, blood tests showed abnormal thyroid values and elevated lipase. At that time, no thyroid medication was started. Instead, his diet was adjusted and all treats were eliminated. After this change, his lipase returned to normal, and an abdominal ultrasound showed no abnormalities in the pancreas.

Recently, new thyroid tests were performed with the following results:

• Total T4: 0.5 µg/dl (below reference range)
• Free T4: 0.3 ng/dl (below reference range)
• cTSH: 0.03 ng/ml (within reference range)

My veterinarian recommended starting levothyroxine (Levogland) and later performing follow-up testing, including free T4 by equilibrium dialysis, to assess his response and adjust the dose if necessary.

My concern is that Scooby does not show typical hypothyroidism symptoms such as weight gain, lethargy, or skin problems. In fact, he is slightly thinner rather than overweight. I am also worried that starting levothyroxine before performing equilibrium dialysis testing might affect the accuracy of the diagnosis.

My questions are:

1. Is starting levothyroxine justified with low T4 and low free T4 but normal cTSH and minimal clinical symptoms?
2. Does performing free T4 by equilibrium dialysis after starting treatment still have diagnostic value, or is it only useful for dose monitoring?
3. Could this be an early stage of hypothyroidism without clear clinical signs?
4. Would monitoring without treatment be reasonable in this situation, or is starting treatment considered standard practice?
5. Could the previously elevated lipase or metabolic stress have affected thyroid hormone levels?

My main goal is to ensure that my dog receives appropriate treatment and is not medicated unnecessarily, but I also do not want to miss a real underlying thyroid disorder.

Thank you very much for your time and expertise.

[bou]

I know it's expensive, but I would take your dog to another vet for a second opinion. Good luck.