121. Thyroid and Parathyroid Glands question Flashcards
Which artery primarily supplies the cranial portion of the thyroid gland in dogs?
b) Cranial thyroid artery
The external parathyroid gland is usually located at which anatomical site relative to the thyroid gland?
b) Dorsolateral margin
What percentage of cats with hyperthyroidism have bilateral thyroid gland involvement?
c) 70-90%
Which of the following is the most common cause of hyperthyroidism in cats?
b) Multinodular adenomatous hyperplasia
What is the first-line medical treatment for hyperthyroidism in cats?
b) Methimazole
In which breed is primary hyperparathyroidism most commonly seen?
c) Keeshond
What is the preferred treatment for canine thyroid carcinoma if the mass is freely movable?
b) Surgery
What is the most serious complication associated with bilateral thyroidectomy in cats?
b) Hypocalcemia
The primary effect of parathyroid hormone (PTH) is to:
b) Increase calcium levels
Which imaging modality is commonly used to confirm the diagnosis of hyperthyroidism in cats?
c) Scintigraphy with technetium-99m
True or False: The majority of thyroid tumors in dogs are benign adenomas.
FALSE
True or False: In cats, the caudal thyroid artery is often absent.
TRUE
True or False: The cranial thyroid artery is the first major branch of the common carotid artery in dogs.
TRUE
True or False: Calcitonin primarily functions to increase blood calcium levels.
FALSE
True or False: Thyroid hormone (T4) has a longer half-life than triiodothyronine (T3).
TRUE
True or False: Ectopic thyroid tissue is more commonly found in dogs than in cats.
FALSE
True or False: Parathyroid autotransplantation may be necessary if the external parathyroid gland is inadvertently removed during surgery.
TRUE
True or False: Hyperthyroid cats frequently present with hypertension.
FALSE
True or False: Scintigraphy is not effective in distinguishing between benign and malignant thyroid masses in cats.
TRUE
True or False: Hypothyroidism is commonly seen after thyroidectomy in dogs.
FALSE
Describe the anatomical location of the thyroid glands in cats.
The thyroid glands in cats are located along the trachea, typically spanning the third to eighth tracheal rings, with a tan, flat appearance.
What is the function of calcitonin, and where is it produced?
Calcitonin is produced by parafollicular (C-cells) of the thyroid gland and functions to decrease blood calcium levels by inhibiting bone resorption.
What is the primary cause of hyperthyroidism in cats?
The primary cause is benign multinodular adenomatous hyperplasia or adenoma of the thyroid gland.
List two potential complications of thyroidectomy in cats.
Hypocalcemia and laryngeal paralysis.
Explain why methimazole is used in the preoperative management of hyperthyroid cats.
Methimazole is used to achieve a euthyroid state, reducing metabolic stress on the body and minimizing surgical risks.
How does parathyroid hormone (PTH) affect the kidneys?
PTH increases renal calcium reabsorption and decreases phosphate reabsorption.
Why is thyroid scintigraphy performed before thyroid surgery?
To confirm the diagnosis of hyperthyroidism and to localize hyperactive thyroid tissue.
What is the main risk of performing bilateral carotid artery ligation during thyroid tumor removal in dogs?
It can lead to severe hypertension and tachycardia due to loss of baroreceptor function.
What dietary management option is available for cats with hyperthyroidism?
Feeding a low-iodine diet (e.g., Hill’s y/d) to reduce thyroid hormone production.
What are the indications for radioactive iodine therapy in cats with hyperthyroidism?
Radioactive iodine therapy is used to treat hyperthyroidism, particularly in cases with ectopic tissue or when surgery is contraindicated.
Explain the surgical approach to accessing the thyroid glands in dogs.
A ventral midline cervical approach is made from the larynx to the manubrium, separating the sternohyoideus muscles.
List three clinical signs commonly seen in dogs with thyroid carcinoma.
Coughing, dyspnea, and dysphagia.
What is the function of parathyroid hormone (PTH)?
b) Increase calcium levels
Which of the following is a major complication of parathyroidectomy in dogs?
a) Hypocalcemia
What is the most common clinical sign of primary hyperparathyroidism in dogs?
c) Urinary tract infections
Which imaging technique is most useful in detecting parathyroid adenomas?
b) Ultrasound
What is the preferred treatment for primary hyperparathyroidism in dogs?
c) Surgery
True or False: Bilateral thyroidectomy always results in permanent hypothyroidism in cats.
FALSE
What is the primary reason for using methimazole in cats prior to thyroid surgery?
c) Induce a euthyroid state
Which hormone is primarily responsible for increasing calcium absorption in the intestines?
b) Parathyroid hormone
List two clinical signs of hypocalcemia in cats following thyroidectomy.
Facial twitching and tetany.
What is the role of calcitriol in managing hypocalcemia?
Calcitriol increases calcium absorption in the intestines and decreases renal excretion of calcium.
What is the primary concern when treating hyperthyroid cats with methimazole long-term?
Potential side effects such as gastrointestinal upset, liver toxicity, and blood dyscrasias.
Which condition can be masked in cats by hyperthyroidism, making diagnosis difficult?
Chronic kidney disease.
What is the advantage of using radioactive iodine therapy in hyperthyroid cats?
It provides a permanent solution by selectively destroying hyperactive thyroid tissue.
Name one diagnostic test used to differentiate between hyperthyroidism and chronic renal disease in cats.
Serum total T4 concentration measurement.
Describe the impact of thyroid hormone excess on the cardiovascular system in cats.
Thyroid hormone excess leads to tachycardia, murmurs, and can cause hypertrophic cardiomyopathy.
Why might a beta-blocker be used in hyperthyroid cats preoperatively?
To control tachycardia and reduce cardiac workload.
How does thyroid hormone influence metabolism in the body?
It increases the basal metabolic rate and affects nearly every organ system.
Which diagnostic test is considered the gold standard for diagnosing hyperthyroidism in cats?
Serum total T4 concentration measurement.
What are the common metastatic sites for thyroid carcinoma in dogs?
Lungs and regional lymph nodes.
Explain the importance of the recurrent laryngeal nerve during thyroidectomy.
Damage to this nerve can result in laryngeal paralysis, affecting breathing and voice.
What is the role of the cranial thyroid artery in thyroid surgery?
It provides the main blood supply to the cranial portion of the thyroid gland.
Name one imaging modality used to detect ectopic thyroid tissue.
Scintigraphy.
What is the significance of finding ectopic parathyroid tissue in a cat during surgery?
It can affect calcium regulation and may require additional surgical management.
Describe the process of parathyroid autotransplantation.
The parathyroid gland is transplanted into nearby muscle tissue to restore function if blood supply is compromised.
What are the two main hormones secreted by the thyroid gland?
Thyroxine (T4) and triiodothyronine (T3).
Why is calcium gluconate used in managing acute hypocalcemia?
It quickly increases serum calcium levels to alleviate symptoms of hypocalcemia.
Which breed of dog is genetically predisposed to primary hyperparathyroidism?
Keeshond.
True or False: Hyperthyroidism in dogs is usually associated with benign thyroid tumors.
FALSE
How does dietary iodine restriction help manage hyperthyroidism in cats?
It limits iodine availability, reducing thyroid hormone synthesis.
What is a potential risk of thyroidectomy in dogs with large, invasive tumors?
Severe hemorrhage due to high vascularization of the tumor.
List two non-surgical management options for hyperthyroidism in cats.
Methimazole therapy and iodine-restricted diet.
Which surgical technique is associated with the highest risk of hypocalcemia in cats after thyroidectomy?
b) Extracapsular
What is the major mechanism by which T3 affects cellular metabolism?
c) Enhancement of gene transcription
What percentage of dogs with thyroid carcinomas develop metastasis during the course of the disease?
d) 80%
In dogs, what is the most common clinical sign of a functional thyroid carcinoma?
b) Weight loss
What diagnostic test is used to differentiate between thyroid and non-thyroid cervical masses in dogs?
a) Fine needle aspirate cytology
Which hormone is responsible for the negative feedback regulation of thyroid-stimulating hormone (TSH) secretion?
b) Thyroxine
Which of the following is the least likely site for metastasis of canine thyroid carcinoma?
d) Spleen
In cats, what is a common side effect of long-term methimazole therapy?
b) Thrombocytopenia
What is the typical histopathological feature of feline hyperthyroid adenomas?
b) Adenomatous hyperplasia
Which procedure is recommended for cats with suspected ectopic thyroid tissue after unsuccessful thyroidectomy?
c) Radioactive iodine therapy
True or False: Laryngeal paralysis is a potential complication of thyroidectomy in dogs.
TRUE
True or False: Dogs with non-functional thyroid tumors often present with symptoms of hyperthyroidism.
FALSE
True or False: Thyroid carcinoma is more common in cats than in dogs.
FALSE
True or False: Thyroid scintigraphy can identify both ectopic thyroid tissue and thyroid carcinomas.
TRUE
True or False: Hyperparathyroidism can lead to fibrous osteodystrophy in dogs.
TRUE
What clinical condition is commonly associated with primary hyperparathyroidism in dogs?
c) Hypercalcemia
How is hypocalcemia managed in cats after bilateral thyroidectomy?
b) Intravenous calcium gluconate
What diagnostic test is most useful for confirming hyperparathyroidism?
b) Ionized calcium levels
What is the primary reason for performing a modified extracapsular thyroidectomy in cats?
c) To preserve parathyroid function
Which condition may develop in cats after treatment of hyperthyroidism if they have underlying renal disease?
b) Azotemia
What is the most common cause of hypothyroidism in dogs?
b) Lymphocytic thyroiditis
Which medication is used to reduce heart rate in hyperthyroid cats with tachyarrhythmias?
a) Atenolol
Describe the primary goal of parathyroid hormone therapy in hypoparathyroid animals.
To increase serum calcium levels and stabilize neuromuscular function.
What surgical technique is most commonly used to remove a parathyroid adenoma?
b) En bloc excision
How long after parathyroidectomy does parathyroid autotransplantation tissue typically regain function?
b) 7-21 days
What is the function of the isthmus glandularis in dogs?
a) Connects the thyroid glands
What is the role of iodide in thyroid hormone synthesis?
c) It is a precursor for thyroid hormone
What is the function of the isthmus glandularis in dogs?
Connects the thyroid glands
What is the role of iodide in thyroid hormone synthesis?
It is a precursor for thyroid hormone
In which dog breed are thyroid tumors more commonly reported?
Golden Retriever
Which thyroid hormone is primarily secreted by the thyroid gland?
Thyroxine (T4)
What is the most common side effect of radioactive iodine therapy in hyperthyroid cats?
Hypothyroidism
What is a common clinical sign of hypocalcemia in cats post-thyroidectomy?
Seizures
Which structure is most likely to be damaged during thyroidectomy, leading to vocal changes in dogs?
Recurrent laryngeal nerve
What is the first-line treatment for hypercalcemia in dogs with primary hyperparathyroidism?
Parathyroidectomy
True or False: Feline hyperthyroidism is often associated with weight gain.
FALSE
True or False: Thyroid carcinoma in dogs is frequently non-functional.
TRUE
What is the primary action of calcitriol in calcium homeostasis?
Increase intestinal absorption of calcium
What is the effect of parathyroid hormone (PTH) on phosphorus levels in blood?
Decreases phosphorus
What is the mechanism of action of methimazole in cats?
Inhibits thyroid peroxidase enzyme
Which imaging modality is best for localizing parathyroid adenomas in dogs?
Ultrasound
What is the most common complication associated with bilateral thyroidectomy in dogs?
Hypothyroidism
Why is scintigraphy preferred for evaluating thyroid function in cats?
It measures iodine uptake
What is the most likely cause of increased serum ionized calcium levels in a dog?
Hyperparathyroidism
What is the main clinical concern when using radioactive iodine treatment in cats with hyperthyroidism?
Development of hypothyroidism
True or False: Ectopic thyroid tissue can be found along the aorta in cats.
TRUE
What is a common presenting sign in dogs with thyroid carcinoma?
Coughing
How is parathyroid hormone (PTH) secretion regulated?
By serum calcium levels
What is the function of the cranial thyroid artery?
Supplies blood to the cranial pole of the thyroid gland
What is the typical cause of hyperthyroidism in older cats?
Multinodular adenomatous hyperplasia
Which hormone regulates the secretion of thyroid-stimulating hormone (TSH)?
Thyroxine (T4)
True or False: Hyperthyroidism in dogs is commonly treated with dietary iodine restriction.
FALSE
What is the most common indication for performing a thyroidectomy in cats?
Hyperthyroidism
Which thyroid hormone is more biologically active?
Triiodothyronine (T3)
What is the primary action of thyroid-stimulating hormone (TSH)?
Stimulate thyroid hormone release
What is the role of the carotid sheath in thyroid surgery?
Contains the common carotid artery, jugular vein, and vagosympathetic trunk
Which of the following hormones is involved in calcium homeostasis?
Calcitonin
What is the most common type of thyroid neoplasm in dogs?
Adenocarcinoma
True or False: Cats with hyperthyroidism may present with increased appetite and weight loss.
TRUE
True or False: Parathyroid hormone decreases calcium reabsorption in the kidneys.
FALSE
What is the main purpose of using beta-blockers in hyperthyroid cats?
Reduce heart rate
Which imaging technique is most useful for detecting thyroid carcinoma metastasis in dogs?
CT scan
What is the significance of measuring free T4 levels in cats with suspected hyperthyroidism?
It helps confirm borderline cases
What is the effect of hyperthyroidism on blood pressure in cats?
Increases blood pressure
True or False: Thyroid carcinoma in dogs is usually non-functional.
TRUE
Which artery supplies the caudal portion of the thyroid gland in dogs?
Caudal thyroid artery
What is the primary cause of hypothyroidism in cats?
Thyroidectomy
Which of the following conditions can be masked by hyperthyroidism in cats?
Renal disease
What is the role of the cranial laryngeal nerve in thyroid surgery?
Controls the vocal cords
How does parathyroid hormone (PTH) affect bone?
Stimulates bone resorption
True or False: Methimazole therapy in cats can cause liver toxicity as a side effect.
TRUE
What is the first clinical sign of hypocalcemia in dogs post-parathyroidectomy?
Tremors
Which condition is associated with excessive production of parathyroid hormone?
Hyperparathyroidism
What is the purpose of using scintigraphy in hyperthyroid cats?
Localize active thyroid tissue
True or False: Dogs with thyroid adenomas usually require lifelong thyroid hormone supplementation.
FALSE
What is the effect of parathyroid hormone on renal phosphorus excretion?
Increases excretion
Which nerve is at risk of damage during thyroidectomy, potentially leading to Horner’s syndrome?
Sympathetic trunk
What is the typical treatment for a canine thyroid tumor that is freely movable?
Surgical excision
Which enzyme is inhibited by methimazole in hyperthyroid cats?
Thyroid peroxidase
True or False: Hyperthyroidism in cats can lead to hypertrophic cardiomyopathy.
TRUE
Which hormone is primarily responsible for increasing blood calcium levels?
Parathyroid hormone
What is the preferred imaging modality to assess the extent of thyroid carcinoma in dogs?
CT scan
What is the most common clinical sign in cats with hyperthyroidism?
Weight loss
Which structure is at risk during thyroidectomy due to its proximity to the thyroid gland?
Carotid sheath
What condition is most commonly associated with increased levels of ionized calcium in dogs?
Hyperparathyroidism
Which hormone decreases in response to elevated calcium levels?
Parathyroid hormone
True or False: Ectopic thyroid tissue can be functional and cause hyperthyroidism.
TRUE
Which artery supplies blood to the external parathyroid glands in dogs?
Cranial thyroid artery
What is the function of thyroglobulin within the thyroid gland?
Precursor to thyroid hormones
What is the effect of parathyroid hormone on bone?
Stimulates bone resorption
Which condition is treated with methimazole in cats?
Hyperthyroidism
What is a common side effect of methimazole therapy in cats?
Vomiting
Which of the following is a clinical sign of hypocalcemia in dogs?
Seizures
What is the primary risk associated with bilateral thyroidectomy in cats?
Hypoparathyroidism
What is the function of the thyroid nerve in dogs?
Controls the thyroid hormone release
True or False: Thyroid scintigraphy is used to evaluate thyroid gland function in hyperthyroid cats.
TRUE
What is the role of calcium gluconate in the treatment of hypocalcemia?
Rapidly raises blood calcium levels
Which breed is most commonly associated with primary hyperparathyroidism?
Keeshond
What is the effect of calcitriol on calcium levels?
Increases calcium absorption
Which clinical sign is commonly associated with thyroid carcinoma in dogs?
Dyspnea
Which hormone is monitored after parathyroidectomy to prevent hypocalcemia?
Parathyroid hormone
True or False: Cats with hyperthyroidism often present with decreased appetite.
FALSE
What is the mechanism by which thyroid hormone influences metabolism?
Increase in cellular oxygen consumption
What is a common complication of untreated hyperthyroidism in cats?
Hypertrophic cardiomyopathy
What influences metabolism?
b) Increase in cellular oxygen consumption
What is a common complication of untreated hyperthyroidism in cats?
b) Hypertrophic cardiomyopathy
Which medication is commonly used to treat hypercalcemia in dogs with primary hyperparathyroidism?
d) Pamidronate
True or False: Parathyroid hormone decreases the reabsorption of calcium in the kidneys.
FALSE
Which structure runs medial to the thyroid gland and can be at risk during surgery?
b) Recurrent laryngeal nerve
What is the expected outcome of administering radioactive iodine (I-131) therapy in cats with hyperthyroidism?
b) Permanent destruction of hyperactive thyroid tissue
What is the most common side effect of radioactive iodine therapy in cats?
a) Hypothyroidism
Which hormone stimulates the absorption of calcium in the intestines?
c) Calcitriol
What is the role of the internal jugular vein in thyroid surgery?
b) Drains blood from the thyroid gland
Which condition is characterized by low blood calcium levels due to parathyroid dysfunction?
b) Hypocalcemia
What effect does thyroid hormone have on the cardiovascular system?
b) Increases cardiac output
True or False: Dogs with thyroid carcinoma often present with polyuria and polydipsia.
FALSE
What is the role of thyrotropin-releasing hormone (TRH) in the body?
a) Stimulate TSH secretion
What is a common clinical sign of hypocalcemia in cats?
b) Muscle tremors
What is the recommended approach for treating cats with bilateral thyroid disease?
b) Radioactive iodine therapy
Which condition is associated with increased levels of TSH despite normal thyroid hormone levels?
c) Euthyroid sick syndrome
What is the effect of hyperthyroidism on glucose metabolism in cats?
c) Hyperglycemia
Which hormone decreases blood calcium levels by inhibiting bone resorption?
a) Calcitonin
True or False: Hypothyroidism in dogs often results in weight gain and lethargy.
TRUE
Which medication is preferred for long-term management of hyperthyroidism in cats that cannot undergo surgery?
c) Methimazole
What is the function of the caudal deep cervical lymph nodes in relation to the thyroid gland?
c) Drain lymph
What is the role of iodine in thyroid hormone synthesis?
b) Serves as a precursor for thyroid hormones
What is a potential complication of staged bilateral thyroidectomy in cats?
a) Severe hypocalcemia
True or False: Cats treated with radioactive iodine are at risk of developing hypothyroidism over time.
TRUE
What is the main function of the thyroid nerve?
b) Stimulation of thyroid hormone release