Hormone tests (thyroid, cortisol, progesterone)
Thyroid hormone measurements, cortisol tests for adrenal disease and progesterone for planning mating and whelping, either on site or sent to an external laboratory.
What it involves
Hormone tests measure hormone concentrations in the blood and allow us to diagnose diseases of the endocrine glands and plan breeding. We most often measure: total T4 and TSH (thyroid in dogs and cats), cortisol in dynamic tests — ACTH stimulation and dexamethasone suppression (Cushing's and Addison's disease), progesterone (timing of ovulation in a bitch, whelping date, risk of miscarriage) and, as needed, fructosamine, insulin, oestradiol or testosterone.
We carry out some tests in our laboratory the same day (progesterone, T4); more complex panels we send to a reference laboratory. Dynamic tests require giving a drug and taking blood at strictly defined intervals, so they take place in the practice.
A single hormone result is rarely enough for a diagnosis — hormones vary during the day, under stress and with other diseases. The veterinarian interprets it together with the symptoms and basic tests.
When it is used
We order thyroid tests in dogs that are overweight, lethargic and losing hair, and in senior cats with weight loss and increased appetite; cortisol tests — with increased thirst, a “pot-bellied” abdomen, thin skin or recurrent episodes of weakness; progesterone — in bitches before mating (from day 5–7 of the heat, every 2–3 days) and in late pregnancy, to predict whelping or plan a caesarean section.
Animals already being treated (thyroid tablets, trilostane) need hormone monitoring every 3–6 months or after every dose change.
Indications: symptoms that should prompt a visit
- A dog is gaining weight, is sluggish, feels the cold and is losing hair on its flanks.
- An older cat is losing weight despite a huge appetite, is restless and has a fast heart rate.
- A dog drinks a great deal, pants, has a pendulous abdomen and thin skin.
- A young dog has recurrent episodes of weakness, vomiting and trembling.
- A bitch is in heat and you want to time the mating correctly.
- A bitch is at the end of pregnancy and you want to know when to expect whelping.
- An animal treated for thyroid disease or Cushing's needs its dose checked.
Conditions for which we use it in particular
Diagnostics beforehand
Before a hormone test we do a blood count, biochemistry and often a urine test — other diseases (e.g. of the kidneys, inflammation) lower T4 and can give a false picture of hypothyroidism. The veterinarian asks about medication, because steroids, some antibiotics and antiepileptic drugs alter hormone results.
For cortisol tests the animal should be fasted and as calm as possible; for progesterone there are no special requirements, but sampling has to be repeated at set intervals.
How it proceeds
A simple measurement (T4, TSH, progesterone) is a blood sample during an ordinary visit; the result from our laboratory the same day, from a send-out laboratory in 1–3 days. ACTH stimulation test: a blood sample, an injection, a second sample after an hour — the animal spends about 1,5 hours with us. Dexamethasone suppression test: samples at the start, after 4 and after 8 hours — a whole day in the practice, in a quiet kennel.
The veterinarian discusses the result by telephone or at a visit and decides on treatment or next steps (e.g. an ultrasound of the adrenal glands to distinguish a pituitary tumour from an adrenal one).
Aftercare
After the blood sample the animal goes home without restrictions; after the dexamethasone test it may be thirstier for a day. If we have started treatment, please stick strictly to the medication times — we usually re-check hormones after 4–6 weeks, and for thyroid monitoring we schedule the blood sample 4–6 hours after the tablet is given.
When planning mating, we arrange the timing of further samples from day to day; the result is available the same day — please contact us for the result.
Frequently asked questions
Does a dog need to fast for a thyroid test?
We recommend fasting for 8–12 hours, because we run blood biochemistry at the same time. If the dog is already taking thyroid tablets, we plan the blood sample 4–6 hours after the dose.
How long does a Cushing's test take?
ACTH stimulation test about 1,5 hours, dexamethasone suppression test about 8 hours. The animal waits with us in a quiet kennel; it can be collected after the last sample.
When should progesterone be tested in a bitch?
We start around day 5–7 of the heat and repeat every 2–3 days until the result indicates ovulation. We then set the best day for mating or insemination.
Does stress affect hormone results?
Yes — cortisol rises with stress, and T4 falls with any more serious illness. That is why we interpret the tests together with the clinical picture and sometimes repeat them.
We manage every case individually. The scope, indications and course described above are indicative; we agree the exact diagnostic and treatment plan during the consultation. This content is for information only and does not replace a veterinary consultation.
Have questions about hormone tests?
Call us or book a consultation. We will set out the diagnostic and treatment plan in writing, before you decide.