Blood sugar, thyroid, and the minerals under hormonal control.
The metabolic and endocrine markers report on how the body fuels and regulates itself — and many of them are best understood as clues that point at a gland, not as ends in themselves.
Glucose is blood sugar, central to diabetes, but a single value is easily thrown by stress (especially in cats), which is why fructosamine — a two-to-three-week average — is used to confirm the picture. Total T4 sets the body's metabolic pace, and the direction it moves points to opposite diseases in the two species: low in the underactive canine thyroid, high in the overactive feline one. Cholesterol in pets is not a heart-attack risk but a signpost to thyroid, adrenal and diabetic disease. And calcium sits under such tight hormonal control that a persistent abnormality is a message worth following to its source.
The recurring theme is that these numbers rarely stand alone: glucose is confirmed by fructosamine, T4 by free T4 and the clinical signs, a high cholesterol by the endocrine screen it hints at, and calcium by its ionised fraction. Read as a set — and tracked over time — they turn scattered clues into a diagnosis.
Glucose is blood sugar, central to screening for diabetes. A single high reading is hard to interpret on its own — stress alone can raise it, especially in cats — so a persistent trend matters more than one value, and fructosamine is used to confirm the picture.
Fructosamine reflects the average blood glucose over the previous two to three weeks, so it sees straight through the momentary spikes — especially stress spikes in cats — that make a single glucose reading hard to trust. It's the number used to confirm diabetes and to judge whether treatment is working.
T4 (thyroxine) is the main thyroid hormone, and it sets the body's metabolic pace. The direction of an abnormal result points to different diseases in the two species — a low T4 raises underactive thyroid in dogs, a high T4 raises overactive thyroid in older cats — so which way it moves is the whole message.
Unlike in people, cholesterol in dogs and cats is read mainly as a clue to hormonal and metabolic conditions — thyroid disease, Cushing's, diabetes — rather than as a heart-attack risk. So a high cholesterol is a prompt to look at the endocrine system, not the arteries.
Calcium is held under tight hormonal control, so a persistently abnormal value — high or low — is meaningful and points to hormonal, kidney or, less often, cancer-related processes. Both extremes matter, and a truly abnormal calcium usually earns a focused work-up.
TSH is the pituitary's instruction to the thyroid, so it moves in the opposite direction to thyroid hormone. In dogs it is the key partner to T4 for confirming an underactive thyroid — a low T4 with a high TSH is the classic combination — and it's the test that helps separate true hypothyroidism from illness-related dips.
Triglycerides are the main fat carried in blood. The commonest reason for a high result is simply a recent meal, so a fasted sample is essential — but a genuinely high fasted triglyceride is worth taking seriously, because it is linked to pancreatitis and points towards hormonal and metabolic conditions.
Cortisol is the body's main stress hormone, and a single resting measurement is almost never diagnostic — it fluctuates far too much. Adrenal disease is diagnosed with dynamic tests (ACTH stimulation, LDDST) that watch how cortisol responds to a challenge, which is what makes the result interpretable.
Ionised calcium is the free, biologically active fraction of calcium — the part that actually does the work. Because total calcium is heavily influenced by albumin, ionised calcium is the measurement that confirms whether an abnormal total is real, and it's the one that matters clinically.
Magnesium is a cofactor for hundreds of enzymes and is essential for nerve, muscle and heart function. Because almost all of it sits inside cells, the blood level understates true status — but a low magnesium matters, not least because it can make a low potassium or calcium refuse to correct.
Free T4 is the unbound, active fraction of thyroid hormone — the part actually available to the tissues. Because it's less swayed by unrelated illness than total T4, it's used to confirm a thyroid picture that total T4 has raised, and to see past the 'sick euthyroid' trap.
The UCCR measures cortisol in urine, corrected for concentration, giving an integrated picture of cortisol output rather than a single stressed snapshot. It is a very sensitive screen for Cushing's disease — excellent at ruling it OUT, but poor at ruling it in, because stress alone raises it.