E: practice questions (week 7)

DM, thyroid disease (presentation, testing, BW, treatment), calcium + additional endo, equine endocrinology

What are the clinical signs of hypoglycemia?

• Lethargy + Weakness

• Lack of Coordination

• Tremors

• Seizures

• Coma

What are the common causes of hypoglycemia in animals?

• Decreased Glucose Production → due to liver disease, inherited enzyme deficiencies, starvation, or malabsorption

• Increased Glucose Use → excessive insulin release (ex: insulinoma), decreased insulin antagonism (ex: hypoadrenocorticism), or increased glucose utilization by tissues (ex: sepsis, strenuous exercise)

• Artifactual Hypoglycemia → falsely low glucose readings due to improper sample handling, such as delayed separation of serum from cells or bacterial contamination

What are some specific examples of conditions that can cause hypoglycemia?

-Insulinoma → tumor of the pancreas that produces excess insulin, leading to rapid glucose uptake by cells

-Hypoadrenocorticism (Addison's Disease) → deficiency of adrenal hormones, leading to decreased gluconeogenesis + increased insulin sensitivity

-Sepsis → severe systemic infection that can impair liver function + increase glucose utilization

-Bovine Ketosis (Type I) → metabolic disorder seen in dairy cows during early lactation, characterized by high energy demands for milk production + insufficient glucose supply

-Ovine Pregnancy Toxemia → condition affecting pregnant ewes carrying multiple fetuses, characterized by inadequate energy intake + severe hypoglycemia

Which hormone plays a major role in maintaining adequate blood glucose levels in long-standing hypoglycemic situations?

Cortisol → long-term controller of glucose levels by inducing gluconeogenesis + insulin resistance

A 12yo spayed obese cat presents with polyuria, polydipsia, & weight loss despite an increased appetite. Bloodwork reveals persistent hyperglycemia + elevated serum fructosamine levels. What is the most likely pathological cause of the hyperglycemia?​

Diabetes mellitus (Type 2)

How can sepsis lead to hypoglycemia in a blood sample?

Increased glucose utilization by cells + bacteria

What is the most consistent chemistry finding in dogs with hypothyroidism?

Hyperlipidemia (increased triglycerides + cholesterol)

What is the #1 pathognomonic clinical sign of PPID in horses?

Hypertrichosis (hirsutism)

A 10yo cat has weight loss + PU/PD. Hospital BG is 320mg/dL with 2+ glucosuria, but the cat was extremely distressed. What is the best next step?

Confirm sustained hyperglycemia with fructosamine &/or home monitoring

Concurrent persistent ________ + ________, usually compatible with clinical signs, establishes diabetes in dogs.

Hyperglycemia, Glucosuria

What diagnostics can we use to stage diabetes in small animals?

Ketones/BHB, Electrolytes, Hydration status, Acid-base status

What blood test used in diabetic animals can be used early as a quantitative assessment of ketoacidosis (DKA detection), but must be interpreted with clinical status + treatment type?

Blood BHB (beta-hydroxybutyrate)

What is an important limitation to using blood glucose levels in small animals to read current glucose, glucose curves, & monitor for hypoglycemia?

Spot values do not describe duration or variability of glucose levels

What can a fructosamine blood test tell us & what are its limitations?

Average glycemia over ~7-10 days + trend monitoring

-Limitations: affected by protein turnover/concentration, misses brief excursions, hyperthyroidism falsely decreases results

How often should we monitor diabetic patients after starting insulin therapy?

Early re-check 5-14 days after starting insulin (or changing dose) to assess NADIR + duration with glucose curve

-after initial re-check, assess if clinical signs reappear (weight loss, PU/PD) or hypoglycemia appears

-periodic review to assess weight + fructosamine

What is the typical feline NADIR target during a blood glucose curve?

80-150mg/dL

An insulin-treated cat is clinically improved. A home curve shows a NADIR of 48mg/dL; all other values are 95-260mg/dL. What is the best action?

Decrease the insulin dose bc hypoglycemia occurred

Since euglycemia does not exclude ketoacidosis, what test is even more important than glucose curves during the first 2 weeks of treatment with SGLT2 inhibitors (Bexacat, Senvelgo) in a diabetic cat?

Blood BHB → test before treatment, at days 2-3, day 7, day 14, day 30, & then every 3 months after that

If clinical signs of diabetes are controlled, but a dog on insulin therapy shows an occasional BG >300, what should be done?

May still be acceptable, do not increase dose from this alone

If a diabetic dog on insulin therapy is still showing clinical signs, but has an acceptable NADIR on a glucose curve, what should be done?

Duration may be too short → review curve/CGM + insulin choice

A cat receiving an SGLT2 inhibitor for 5 days develops vomiting + lethargy. BG is 160mg/dL. What is the most important immediate next step?

Measure blood BHB + assess for euglycemic DKA

What are the main clinical signs in small animals with diabetes mellitus?

PU/PD, polyphagia, weight loss

What are some of the behavioral changes that may occur in animals affected by hypoglycemia, which owners treating pets with diabetes should be informed about?

Ataxia, Depression, Ptyalism

If a diabetic animal must undergo a surgical procedure, how should owners administer their insulin prior to surgery?

Since must be NPO, give ½ dose of insulin only → ensure this is the 1st surgery performed of the day

-give 5% dextrose in fluids during procedure

If an owner is having trouble getting their diabetic pet regulated on insulin at home, what else should be considered?

Concurrent diseases → HAC, hypo/hyperthyroidism, UTIs, pancreatitis, hepatic lipidosis, acromegaly

How will you know if a cat is insulin resistant?

Glucose curve will be basically flat → if giving >2.2u/kg with no response, they are resistant

Why might a diabetic cat that is on >2u/kg of insulin still be unregulated?

Incorrect insulin handling/administration OR Concurrent disease present

The Somogyi Effect explains that if the body has periods of severe _________, you will see a rebound _________. Because of this, owners will notice a return of clinical signs + glycosuria, & spot glucose measurements will show severe _________.

Hypoglycemia, Hyperglycemia, Hyperglycemia

A cat with hyperadrenocorticism will always have what other disease concurrently?

Diabetes mellitus

25-28% of cats (mainly older males) with diabetes mellitus will also have what other disease?

Acromegaly → excess GH from a GH-secreting tumor (macroadenoma most likely)

-100% of cats with acromegaly will also have DM

What are the main clinical signs of acromegaly?

PU/PD, polyphagia, weight gain (could start with loss), stridor, prognathia inferior, abdominal enlargement/organomegaly, clubbed paws, neuro signs

What are the typical blood work findings in a cat with acromegaly?

Hyperproteinemia, Hyperglycemia, Glucosuria

What are the different diagnostics that can be used to diagnose acromegaly in small animals?

Bloodwork, CT/MRI, IGF-1 levels

A older male cat presents with the following subset of diseases: diabetes mellitus, renal disease, cardiomyopathy, stridor, & conformational changes. What is your top differential diagnosis?

Acromegaly

What is the treatment for acromegaly in dogs?

Spay → more common in older intact females

What are the treatment options for acromegaly in cats?

-Hypophysectomy → surgical removal, 85% of DM won’t need insulin now

-Radiation therapy → variable response, will recur in 12-24 months

-Medical → Cabergoline or Pasireotide

What is the prognosis for animals with acromegaly?

Short term: Guarded to good

Long term: Poor

-MST 4-60 months

What are the anti-insulin hormones?

Cortisol, growth hormone, epinephrine, glucagon, ± progesterone

What is the cause of 50% of primary hypothyroid cases in dogs, where we see leakage of thyroglobulin, fibrosis, & inflammation of the thyroid glands?

Lymphocytic thyroiditis (immune-mediated)

What is the cause of secondary hypothyroidism in dogs?

Rare pituitary malformation/neoplasia

What is known as congenital hypothyroidism in dogs, caused by a rare severe deficiency of thyroid hormones from birth or early puppyhood?

Cretinism

Which breeds may be able to inherit hypothyroidism?

Beagle, Borzoi, Danes, OESD

What are the common clinical signs of hypothyroidism?

Weight gain, lethargy/mental dullness, derm issues (seborrhea, rat tail, poor wound healing), heat seeking, bradycardia, constipation, muscle weakness/atrophy, edema

What is the cause of myxedema, which is a rare clinical sign of hypothyroidism?

Hyaluronic acid deposition into the eyelids, cheeks, + forehead

-may be precipitated by infectious disease, depressant drugs, heart failure, or shock

What are the main clinical signs seen in a dog with cretinism?

Mental retardation, stunted/disproportionate growth, large broad heads, macroglossia, hypothermia, delayed dental eruption

What might we find upon obtaining a CBC/Chem in a dog with hypothyroidism?

-Fasting hypercholesterolemia → increased high-density lipoproteins (HDLs)

-Hypertriglyceridemia → increased low + very low-density lipoproteins (LDLs/VLDLs)

-Mild non-regenerative anemia

What is the first-line screening test with high sensitivity for both hypothyroidism + hyperthyroidism?

Total T4 (TT4) → protein-bound + free circulating T4

What are the diagnostic tests for hypothyroidism, which are helpful for when TT4 is on the low end of the reference range when clinical signs are present?

-Free T4 by equilibrium dialysis → unbound biologically available T4

-TSH → pituitary response to circulating thyroid hormones

What is the diagnostic test used to detect thyroiditis in dogs?

TgAA → shows thyroid autoantibodies

Why is hypothyroidism over diagnosed in dogs?

Non-thyroidal illness syndrome (euthyroid sick syndrome)

What is the definition of test sensitivity?

The ability of a diagnostic test to correctly identify people who have a specific disease or condition

-measures the true positive rate as well as false negative

-highly sensitive test (100% sensitivity) with a negative result helps rule out the disease because it rarely produces false negatives

What is the definition of test specificity?

Statistical measure of a test's ability to correctly identify people who do not have a condition or disease

-measures the true negative rate as well as false positives

-high specificity (100% specific test) helps "rule in" a disease when a patient gets a positive result

What will happen to the positive predictive value of a test if the prevalence of a disease is low?

Decreases → will see more false positives + lower probability of actual disease in the population

What type of tumor will be seen in neoplasia that causes hypothyroidism?

Large, non-functional invasive follicular carcinoma

-BLEED excessively + metastasize

-poor prognosis

What is the treatment for canine thyroid neoplasia?

Surgical removal + chemo + radiation (sometimes I-131)

What is the most common endocrine disorder of cats?

Hyperthyroidism

What is the most common cause of hyperthyroidism in cats?

Bilateral functional thyroid adenoma

What is one of the main consequences of untreated hyperthyroidism in cats?

CKD → renal hypertension, increased GFR, sclerosis

What are the common clinical signs of hyperthyroidism?

Weight loss, polyphagia, hyperactivity, tachycardia, PU/PD, V/D, systolic murmur, blindness, palpable thyroid, aggressive, unkempt fur

What will the CBC/Chem look like in a cat with hyperthyroidism?

CBC: Erythrocytosis, Increased MCV, Leukocytosis, Lymphopenia, Eosinopenia

Chem: Increased ALT + ALP + LDH + AST + Glucose + Azotemia + Phosphorus + Bilirubin

What ECG findings might you see in a cat diagnosed with hyperthyroidism?

Tachycardia, Increased R wave, Ventricular arhythmias

What are some of the diseases that may mimic OR occur concurrently to hyperthyroidism?

DM, CKD, Cardiomyopathy, Hepatic disease, Maldigestion/malabsorption, Neoplasia, CNS disease

What diagnostic test to diagnose hyperthyroidism is useful in cats that have no thyroid slip?

Technesium-99

An older dog presents with clinical hypothyroidism (typical clinical signs) as well as a low TT4. What should be your next step?

Measure fT4 + TSH to confirm diagnosis → treat with Levothyroxine → monitor levels to look for clinical improvement + serial TT4 testing 4 weeks after starting meds, then every 6-12 months after that

An older dog presents with no clinical signs of hypothyroidism, but a low TT4. What should you do next?

Review history + medications (glucocorticoids, phenobarbital) → evaluate for NTIS (euthyroid sick syndrome) → monitor for clinical signs + retest if indicated

An older dog presents with clinical hypothyroidism (typical clinical signs), but a normal TT4. What should be your next steps?

Evaluate for NTIS → perform fT4, TSH, ± anti-T4 autoantibodies → treat with Levothyroxine if diagnosis confirmed → monitor TT4 levels after 4 weeks of treatment, then every 6-12 months after that

An older cat presents with clinical hyperthyroidism + an elevated TT4. How should you proceed?

Recommend treatment options for FHT

An older cat presents with clinical hyperthyroidism, but a normal TT4. What should be your next steps?

Test TT4 + fT4 2-4 weeks after initial test → evaluate for non-thyroidal disease → consider T3 suppression or thyroid scintigraphy

An older cat presents with an enlarged thyroid gland, but has no clinical signs of hyperthyroidism + a normal TT4. How should you proceed with this cat?

Monitor clinical signs → repeat T4 test in 6 months

An older cat presents with some physical exam findings suggestive of hyperthyroidism + an elevated T4. What should you do next?

Repeat T4 in 2 weeks → if T4 elevated = treat; if T4 normal = re-evaluate in 6 months

An older cat presents with an elevated T4, but no clinical signs of hyperthyroidism or any palpable nodule. What should you do next?

Repeat/confirm T4 → if T4 elevated = treat; if T4 normal = re-evaluate in 6 months

What is the recommended treatment for hypothyroidism?

L-thyroxine → normalizes T3 + T4 with very low risk for creating hyperthyroidism

-0.02mg/kg PO q12h

How often should you recheck a newly diagnosed hypothyroid dog after starting treatment with Levothyroxine, & what should we expect to see at these rechecks?

1. 1-2 weeks → should see improved activity

2. 4-6 weeks → should see improved hair coat

3. 4-8 weeks (at one month, then every 6 months) → should just need therapeutic monitoring from now on

What is the prognosis of hypothyroidism with treatment in dogs?

Good

What is the recommended treatment for unilateral hyperthyroidism in cats?

Surgical removal

-could potentially lead to hypoparathyroidism if removed, especially if bilateral removal is performed

What is the recommended treatment for bilateral hyperthyroidism in cats?

Methimazole, I-131 radiation therapy, or Hill’s y/d restricted iodine diet

-may also add B-blockers if cardiomyopathy present or treatment for renal failure if present

How does Methimazole work in the treatment of hyperthyroidism?

Blocks thyroid hormone synthesis + release → prevents iodine incorporation & inhibits coupling of DIT + MIT

What are the benefits of a month-long Methimazole (Tapazole) medical therapy trial?

Unmasks CKD or other concurrent diseases that could kill the cat if left untreated

-should do this prior to trying I-131 therapy also

What is the dose for Methimazole in cats?

2.5-5mg/cat q12h

-recheck cat + TT4 after 2 weeks

What are the main reversible side effects of Methimazole, where if the owner sees these signs, they should stop treatment for a few days then reinstate at a lower dose?

Anorexia, vomiting, lethargy

What are the irreversible (weird) side effects of Methimazole that tell us a cat will absolutely not be tolerant of this treatment?

Facial excoriations, bleeding diathesis, hepatopathy, myasthenia gravis, cold agglutination-like disease

How does I-131 radiation therapy work to treat hyperthyroidism in cats with just one SQ injection?

Selectively destroys active thyroid tissue

-preserves normal tissue (normal gland atrophied due to negative feedback/decreased TSH)

What is the prognosis of hyperthyroidism in cats with proper treatment?

Good → MST 417 days-24 months

What are the two most common reasons for death in hyperthyroid patients, even with treatment?

Renal disease + Neoplasia

A 7yo MN Chow is presented for PU/PD, halitosis, & weight loss. Bloodwork identifies a hypercalcemia + iPTH is measured & returns within the normal range. What is the diagnosis?

Primary hyperparathyroidism

Under normal conditions, what effect should PTH have on serum calcium + phosphorus levels in the body?

↑ Ca + ↓ P

Under normal conditions, what effect should Calcitonin have on serum calcium + phosphorus levels in the body?

↓ Ca + ↓ P

Under normal conditions, what effect should Vitamin D3 have on serum calcium + phosphorus levels in the body?

↑ Ca + ↑ P

What blood value is the best representation of free calcium, so if you are concerned about an abnormal total calcium in a patient, this is what you should evaluate?

Ionized calcium (iCa)

What will the calcium + PTH levels look like in a patient with primary hyperparathyroidism?

↑ Ca + ↑ PTH

What will the calcium + PTH levels look like in a patient with secondary hyperparathyroidism (nutritional/renal)?

↓ Ca + ↑ PTH

What will the calcium + PTH levels look like in a patient with primary hypoparathyroidism?

↓ Ca + ↓ PTH

What will the calcium + PTH levels look like in a patient with hypercalcemia of malignancy?

↑ Ca + ↓ PTH

What are the main hypercalcemia rule-outs?

G → granulomatous disease

O → osteopathy/osteolytic disease

S → spurious

H → hyperparathyroidism

D → hypervitaminosis D

A → addison’s

R → renal disease

N → neoplasia (LSA, AGASACA, MM)

I → idiopathic cats

T → temperature (cats)

What are some of the general therapeutics for acute hypercalcemia?

-FLUIDS → normal saline or buffered isotonic fluids

-Furosemide → inhibits reabsorption, only do if hydrated

-Glucocorticoids → but not if patient has cancer! obscures definitive dx

-Bisphosphonates IV → only if hydrated, lasts a few weeks to stabilize

-additional: Mithramycin, Calcimimetics, Calcitonin (expensive)

What is the main treatment for chronic idiopathic hypercalcemia of felines?

Alendronate (bisphosphonate) → 5-10mg/cat PO once weekly + water

What is the main clinical sign you will notice right before a patient presenting with hypocalcemia has a seizure?

Pawing at face/”itchy face”

What are the main rule-outs for hypocalcemia?

H → hypoparathyroidism. hypovitaminosis D

E → eclampsia

R → renal disease

P → pancreatitis/phosphates (enemas)

E → ethylene glycol toxicity

S → spurious/sepsis

What is typically the cause of primary hyperparathyroidism in small animals?

Benign adenoma

What are the possible causes of secondary hyperparathyroidism?

Nutritional, Renal, Intestinal