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Pathobio > Thyroid Endocrine > Flashcards

Thyroid Endocrine Flashcards

1
Q

Hormones produced in the thyroid

A

T3 -triiodothyronine
T4 -thyroxine
Calcitonin – peptide hormone from C-cells

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2
Q

How is Iodine transported into the follicle

A

Iodide in the blood
–> Na+/I- symporter –> apicial surface Pendrin channel (allows I- into colloid) –> oxidized to Iodine and iodinates Thyroglobulin (tyrosyl residues)

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3
Q

Thyroid cysts

A

Follicular or thyroglossal duct

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4
Q

4 causes of thyroid atrophy

A
  • decreased TSH stimulation
    1. 2ndary to lack of trophic hormone
    2. Immune-mediated destruction
    3. Compression/invasion by neoplasm
    4. Colloid goiter
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5
Q

Causes of Thyroid hyperplasia

A
  1. Iodine deficiency goiter

2. Feline hyperthyroidism

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6
Q

2 types of thyroid neoplasms

A
  1. Follicular cell adenoma/carcinoma

2. C-cell adenoma/carcinoma

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7
Q

Causes of HYPOthryoidism

A
  • 2ndary
  • Goiter
    • Iodine-deficient goiter
    • Iodine-excess or goitrogens
    • Gongenital dyshormonogenetic goiter
  • Follicular atrophy
    • Iatrogenic
    • Idiopathic (autoimmune)
  • Lymphoplasmacytic thryoiditis
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8
Q

Microscopic features of Thyroid atrophy

A
  • cuboidal epithelial cells
  • dense colloid
  • distended follicles
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9
Q

Congenital dyshormonogenetic goiter

A

Symmetrical hyperplastic goiter

  • Hypothyroidism
    • decreased growth rate = stillborn
    • abnormal coat = hairless when born
  • Autosomal recessive -ruminants, dog/cat
    • defective Tgb synth or iodination
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10
Q

Microscopic features of hyperplasic goiter

A
  • follicular epithelium
    - tall columnar
    - forms a papillary projection /endocytic vacuoles
  • follicular lumen
    - Pale colloid
    - narrow follicular lumen
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11
Q

Feline Hyperthyroidism

Thyroid lesions

A
  1. Follicular adenomas

2. Adenomatous hyperplasia

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12
Q

Non-thyroid lesions associated with Feline Hyperthyroidism

A
  1. Increased Phos –> Reciprocal decrease in Ca
  2. Increased PTH (due to low Ca) –> hyperparathyroidism
  3. Hypertrophic cardiomyopathy
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13
Q

Thyroid tumors
(adenoma vs carcinoma?)
in Dog vs Cat vs Horse vs cattle

A 
Dog = carcinoma
Cat = adenoma
Horse = C-cell adenoma --w/o clinical signs
Cattle = C-cell Carcinoma --Dairy bulls
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14
Q

What cell secretes PTH

A

Chief cell

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15
Q

Main target organs of PTH

A
  1. Bone
  2. Renal tubules
    - -Blocks Phos reabsorption
    - -Enhances Ca reabsorption
  3. Intestines

-mobilizes Ca

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16
Q

Stimulating release of PTH

A

Recently synthesized PTH:

  • released directly without entering the storage pool
  • stimulated only by a decreased calcium ion concentration

PTH from the storage pool:

  • mobilized by
    • cAMP and β-agonists
      • epi
      • norepi
      • isoproterenol
    • lowered blood calcium ion
17
Q

Parathyroid gland disorders

A
  1. Parathryoid (Kursteiner’s) cysts
  2. Hyperparathryoidism –Most common
  3. Hypoparathyroidism –Immune-mediated parathyroiditis
18
Q

Causes of Hyperparathryoidism

A
  • Primary
    1. Chief cell adenoma
    2. Chief cell carcinoma
  • Secondary
    1. Nutritional
    2. Renal
19
Q

Causes of Pseudohyperparathyroidism

aka Humoral hypercalcemia of malignancy

A
  1. Lymphoma
  2. Anal sac apocrine carcinoma
  • does not have a true elevation of PTH
  • persistant hypercalcemia
  • should cause atrophy of Parathyroid gland
20
Q

Secondary lesion due to Parathyroid adenoma

A

Severe thinning of cortical bone and large resorptive cavities

21
Q

Lesion seen with Iodine deficiency

A

Early stage or fetus
-Hyperplastic goiter (enlarged, firm, dark red-brown)

After correction of iodine deficiency or maturation of the animal
-progresses to a colloid goiter (involutional stage)

22
Q

Pathogenesis of Feline Hyperparathyroidism

A

IgG acts on TSH receptors –> proliferation of thyroid follicular cells –> multiple hyperplastic nodules or follicular adenomas

23
Q

Common thyroid tumor in Dairy bull

A

Cell cell carcinomas

-Ca-rich diet

24
Q

Pathogenesis: Renal Dz –> Hyperparathyroidism

A
  • Decrease Phos excretion –> hyperphosphatemia –> decreased Ca:P –> stimulates PTH release
  • Decreases Vitamin D3 production –> decrease intestinal absorption of Ca
25
Q

Nutritional imbalances leading to Hyperparathyroid

A
  1. Insufficient Ca
  2. Excess Phos
  3. Cholecalciferol deficiency

Pathobio (12 decks)

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