Endocrine Tumors (Objectives Only)

What signalment of dogs typically develop thyroid neoplasia?

- Older dogs - 9-11 years

What clinical signs are associated with thyroid neoplasia?

- Most dogs present with palpable ventral cervical mass (can be incidental on PE)

- Less common signs include → cough, dyspnea, dysphagia, change in bark, laryngeal paralysis, Horner's syndrome, facial edema

Most thyroid tumors in the dog are benign or malignant? Functional or non-functional?

- Malignant

- Non-functional

Why are some canine patients with thyroid neoplasia actually hypothyroid?

- Secondary to destruction of normal parenchyma

What treatment options are available for thyroid neoplasia when the mass is freely movable? What is the prognosis?

- Surgical excision

- MST of ~ 3 years; but if the tumor is invasive, reported 6-12 months

For non-resectable thyroid tumors or patients with metastatic disease, what treatment options are available?

- Radiation

- Chemotherapy (Palladia, mitoxantrone, doxorubicin, carboplatin)

- Combination treatments

- I131 ablation (must be away from owner for up to 3-6 weeks depending on severity or need for quarantine)

What are some functional adrenal tumors?

- Adrenocortical Adenomas/adenocarcinomas

- Aldosterone-secreting adrenocortical tumors

- Adrenal medullary tumors

Describe the etiology of cushing's.

- Functional cortisol-secreting adrenal cortex tumors are responsible for 15-20% of hyperadrenocorticism (Cushing's)

- Pituitary-dependent accounts for 80-85% of cases

What are clinical signs and BW abnormalities associated with Adrenocortical adenomas/adenocarcinomas?

- Clinical signs: PUPD, polyphagia, lethargy, panting, enlarged abdomen, patchy alopecia, thinning skin, calcinosis cutis

- BW: ACTH/LDDST testing, elevated ALP, hyperglycemia, hypercholesterolemia, stress leukogram

What are clinical signs and BW abnormalities associated with alodsterone-secreting adrenocortical tumors?

- Clinical Signs: Increased BP, PUPD, Fatigue/muscle weakness (Low potassium)

- BW: Hypokalemia, hypernatremia, elevated aldosterone

Describe the typical biologic behavior of adrenal medullary tumors.

- All are malignant

- Vascular invasion is common

What is the signalment of animals most commonly affected by pheochromocytomas?

- Older dogs, males > females

What clinical signs are associated with phenochromocytomas?

- Clinical Signs may be episodic

- Weakness, collapse, panting, anxiety, restlessness, exercise intolerance, poor appetite, PU/PD, weight loss

What physical exam findings are associated with phenochromocytomas?

- May be normal

- Tachypnea

- Tachycardia

- Weakness

- Pallor

- Arrythmias

- Hypertension

What is the treatment of choice for adrenal-dependent HAC?

- Surgery (adrenalectomy; procedure best performed with experienced team (surgeon, internist, criticalist, anesthesiologist)

If surgery is not an option for management of adrenal-dependent HAC, what medical therapies are available?

- Mitotane - Used as true cytotoxic agent (Generally need higher doses than for pituitary dependent HAC and relapses are common)

- Trilostaine - Not cytotoxic but successfully used to manage adrenal-dependent HAC, even in some dogs with metastasis

What management is appropriate for adrenal medullary tumors?

- Pre-op: BP, imaging to look for metastasis and invasion, +/- catecholamine testing

- Peri-op (controversial) management with phenoxybenzamine (non-competitive alpha-adrenergic antagonist)

- Surgery is only definitive therapy

If an adrenal nodule, mass or gland width >10mm is noted on imaging (most often AUS), what steps can you take?

- Consider a functional assessment (ACTH/LDDST)

- Consider AUS/thoracic radiographs to assess for metastasis

- Consider surgery if functional, locally invasive, or >2.5cm

- If smaller than 2cm and non-functional, monitor with serial AUS (1, 2, 4, 6 months...)

Insulinomas in dogs are generally malignant or benign?

- Malignant

What signalment of dogs are commonly affected by insulinoma?

- Medium to large-breed dogs

- Median age 9-10 yrs

What are clinical signs associated with insulinoma?

- Clinical signs associated with low BG -> Weakness, ataxia, collapse, behavior change, seizures, disorientation

What diagnostic findings are associated with insulinoma?

- BW: Documenting hypoglycemia (BG <60 mg/dL) AND concurrent normal or elevated serum insulin conc.

- Imaging (for surgical preparation) -> Thoracic/abdominal radiographs are often unremarkable, but AUS will identify a mass ~50% of the time

For insulinomas, AUS is better at IDing __________ while abdominal CT is better at IDing __________________.

- Metastasis

- Primary lesions

How is insulinoma managed?

- Acute management of hypoglycemia with IV dextrose slow followed by CRI (only if intent to to go to Sx in hosp - difficult to wean off CRI; Caution that CRI can worsen unregulated insulin secretion)

- Sx (Tx of choice) with ex-lap and partial pancreatectomy; Resect suspected metastatic lesions when possible

- Ongoing medical therapy to control hypoglycemia, cytotoxic agents to kill pancreatic beta-cells (streptozocin), dietary modifications, and prednisone