Tylosin (Tylan Rx) seems to be very safe in dogs. It causes problems in ruminants and horses sometimes, but that seems to be related to the fact that they are herbivores with a high dependence on bacterially aided digestion. Tylosin can interfere with lab testing for ALT and AST, so if there are elevations in liver enzymes after starting it there is a possibility it is a lab error produced by the antibiotic. I could not find any reports of toxicity with long term use and tylosin appears to be pretty safe even when overdosed (short term).
Aldosterone response of several factors from a low base value. This factoring indicates secondary hypoaldosteronism (sodium low, potassium and renin enzyme will be low). Usually doubling to quadrupling from a low base aldosterone value is what is seen in secondary adrenal insufficiency. Decoupling of aldosterone in the ACTH stimulation test is possible (. 2 ng/dl stimming to 20).  A result of doubling or more of aldosterone may help in tandem with a cortisol stimulation that doubled or more confirm a diagnosis of secondary adrenal insufficiency. In rare cases, an aldosterone stimulation which did not double, but with the presence of low potassium, low renin and low ACTH indicates atrophy of aldosterone production from the prolonged lack of renin.