Parathyroid Gland Pathology

Question 1

How many parathyroid glands are there typically?

Answer 1

Four, two glands on each lobe of the thyroid gland

Question 2

Anatomical location of parathyroid glands in dogs and cats

Answer 2

Have two external parathyroid glands close to the thyroid gland,
and two internal parathyroid glands beneath the thyroid gland capsule.

Question 3

Anatomical location of parathyroid glands in cattle and sheep

Answer 3

Have two external parathyroid glands in loose connective
tissue close to the thyroid gland and two smaller internal parathyroid glands.

Question 4

Anatomical location of parathyroid glands in horses

Answer 4

Have upper and lower parathyroid glands, the latter of which is located at the level of the first rib.

Question 5

Anatomical location of parathyroid glands in pigs

Answer 5

Have a single pair of parathyroid glands embedded in the thymus or adipose tissue

Question 6

Anatomical location of parathyroid glands in rats

Answer 6

Have a single pair of parathyroid glands close to the thyroid gland.

Question 7

Which types of cells are present in the parathyroid glands? (3)

Answer 7

• Chief (principal) cells secrete PTH (parathyroid hormone) - small polygonal cells with round nuclei and pale-staining cytoplasm.
• Oxyphil cells are sometimes present, more commonly in older individuals - much larger than chief cells.
• (Thyroid C-cells - interstitial cells within the thyroid - secrete calcitonin)

Question 8

Which cells are involved in calcium regulation? (3)

Answer 8

• Chief cells of the parathyroid gland
• C cells of the thyroid gland
• Osteoblasts in bone are sensitive to free plasma calcium ions via their calcium-sensing receptor, a G protein-coupled receptor with an extracellular calcium-sensing domain.

Question 9

Parathyroid hormone function (3)

Answer 9

1) . Mobilises calcium from bone
a. Rapid diffusion from the bone fluid to plasma
b. Increased osteoclast activity
2) . Increased reabsorption of calcium in the distal convoluted tubules & decreased reabsorption of phosphorus in the proximal convoluted tubules
3) . Increased absorption of calcium from the intestine by regulating hydroxylation of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (active Vitamin D) by 1-α-hydroxylase in the kidney

Question 10

Vitamin D function (3)

Answer 10

Question 11

Calcitriol function (3)

Answer 11

Question 12

What is calcitonin? + function (5)

Answer 12

Polypeptide hormone composed of 32 amino acids

Question 13

What is parathyroid hormone-related peptide (PTHrP)? (3)

Answer 13

Question 14

Intestinal calcium absorption - calcium-regulating hormones (3)

Answer 14

PTH - inc

Vitamin D - high inc

Calcitonin - n/a

Question 15

Renal calcium resorption - calcium-regulating hormones (3)

Answer 15

PTH - inc

Vitamin D - inc

Calcitonin - dec

Question 16

Bone calcium mobilisation - calcium-regulating hormones (3)

Answer 16

PTH - high inc

Vitamin D - inc

Calcitonin - dec

Question 17

Renal phosphorus resorption - calcium-regulating hormones (3)

Answer 17

PTH - dec

Vitamin D - inc

Calcitonin - dec

Question 18

Answer 18

Question 19

What is parturient hypocalcaemia? (3)

Answer 19

Question 20

How are cows displayed with parturient hypocalcemia? (2)

Answer 20

• Cattle typically have more recumbency, dogs more tremors/tetany
  
  • Due to differences in function of the neuromuscular junction (NMJ)
  • Transmission of nerve impulses across the NMJ are blocked by hypocalcemia in cows
  • Loss of stabilising nerve membrane-bound calcium leads to spontaneous repetitive firing of motor nerve fibres in dogs
• Cows that recover from milk fever are prone to other metabolic disease.

Question 21

Stages of parturient hypocalcaemia (3)

Answer 21

Question 22

Physiology of parturient hypocalcaemia - calcium regulation

Answer 22

Question 23

Causes of dec calcium conc (hypocalcaemia) (4)

Answer 23

Question 24

Primary hyperparathyroidism (neoplasms of parathyroid glands) (2)

Answer 24

1. Adenoma
2. Carcinoma - uncommon

Question 25

Answer 25

Question 26

Answer 26

Question 27

Microscopic criteria for malignancy (8)

Answer 27

Question 28

Answer 28

Question 29

Secondary hyperparathyroidism (2)

Answer 29

• Secondary nutritional hyperparathyroidism
• Secondary renal hyperparathyroidsim

Question 30

What is secondary nutritional hyperparathyroidism? (6)

Answer 30

Question 31

Answer 31

Question 32

What is secondary renal hyperparathyroidism? (4)

Answer 32

Question 33

Pathogenesis of secondary renal parathyroidism

Answer 33

Question 34

Hyperparathyroidism gross findings (5)

Answer 34

Question 35

Hyperparathyroidism clinical signs (6)

Answer 35

Question 36

Hyperparathyroidism clinical pathology (4)

Answer 36

• PTH prevents reabsorption of phosphorus from brush border of the PCT by inhibiting sodium-phosphate co-transporter
• Inc ALP (alkaline phosphatase - related to bone resorption (bile + bone)), maximum amount in liver, bone, placenta

Question 37

Answer 37

Question 38

Answer 38

Question 39

What is pseudohyperparathyroidism? (4)

Answer 39

Question 40

Answer 40

Question 41

Answer 41

Question 42

Answer 42

Question 43

Causes of hypercalcaemia (acronym) (9)

Answer 43

Hard ions G

Question 44

What is multiple endocrine neoplasia (MEN)?

Answer 44

Question 45

Increased renal production of which of the following occurs during lactation?

Answer 45

Calcitriol

Question 46

What clinical sign is associated with hypocalcemia in dogs?

Answer 46

Tetany

Question 47

Which of the following cells secrete Parathyroid Hormone-related Peptide (PTHrP)?

Answer 47

Cancer cells