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43 Cards in this Set

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Where are the Parathyroid Glands normally located?
Posterior surface of the Thyroid
What is the embryological origin of the Parathyroid glands?
Inferior parathyroids = 3rd Pharyngeal Pouch

Superior = 4th Pharyngeal Pouch
Normal Parathyroid
-cuboidal Chief Cells = synthesize & secrete PTH
What is seen here?
Waterclear cells of Parathyroid
-form of Chief Cell with more abundant, clear PTH secretions in their cytoplasm
What is seen here?
Oxyphil Cells of Parathyroid
-contain numberous, red-staining Mitochondria
-late stage chief cells = no longer secrete PTH
What is seen here?
Waterclear cells of Parathyroid
-form of Chief Cell with more abundant, clear PTH secretions in their cytoplasm
What is seen here?
Oxyphil cell = stuffed with Mitochondria
What is seen here?
Normal adult Parathyroid gland
-interspersed fat cells that increase with relative age
-presence of fat cells helps differentiate from Hyperplastic Parathyroids
What is seen here?
Describe the structure of PTH
84 amino acids in length
-only first 34 are needed for function
What are the 3 main functions of PTH?
1. Mobilize Calcium from Bone by stimulating Osteoclastic resorption

2. Promote renal excretion of Phosphate by decreasing tubular reabsorption of PO4

3. Stimulate 1,25-OH2D3 synthesis by the kidney, thus promoting Ca+ absorption from the gut
What cells produce Calcitonin?
Parafollicular Cells ("light cells") in the Thyroid gland
What are the functions of Calcitonin?
1. Inhibits Osteoclastic resorption of bone
2. Reduced calcium release from bone leads to:
-lower serum Ca++
-compensatory increase in PTH secretion
What stimulates the release of Calcitonin?
elevated free serum Calcium
Thyroid tumor that arises from Parafollicular C cells & secretes Calcitonin
Medullary Carcinoma
Medullary Carcinoma of the Thyroid
-causing tracheal compression

Calcitonin
What is seen here? What does it secrete?
Medullary Carcinoma of the Thyroid
-nests of polygonal cells in an Amyloid stroma
-Parafollicular cell nests are encircled by dense fibrous tissue
-Upper right = psammoma bodies = focal calcifications
What is seen here?
What is Medullary Carcinoma associated with?
MEN II
-Medullary CA of thyroid
-Pheochromocytoma
-Parathyroid Hyperplasia or Adenoma
List the sequence of metabolic events initiated by increased PTH
1. Ca+ is mobilized from bone by Osteoclasts
2. Serum Ca++ rises
3. Urine Ca+ rises
4. Urine PO4 increased by decreased resorption
5. Serum PO4 decreases due to renal loss
6. Serum Alkaline Phosphatase rises (PTH stimulates Osteoblasts)
Resorption of Distal Phalanges
-due to Hyperparathyroidism
What is seen here?
Bone resorption in Hyperparathyroidism = Osteitis Fibrosa Cystica
-Upper left = multinucleated Osteoclasts are digging a resorption pit
-Lower right = Osteoblasts are adding new bone
What is seen here?
Osteitis Fibrosa Cystica
-due to Primary Hyperparathyroidism
-cystic changes in the bone due to osteoclastic resorption
What is seen here?
Liquified focus fo bone resorption in Hyperparathyroidism
What is seen here?
Osteitis Fibrosa Cystica

"Brown tumor" = fibrous replacement of resorbed bone leading to formation of non-neoplastic tumor-like masses
-center = clusters of osteoclasts
-Right = brownish deposits of Hemosiderin
What is seen here?
Metastatic calcification of the kidney due to Hyperparathyroidism
-blue staining, rounded deposits of Calcium Phosphate
-brown deposits of Hemosiderin
What is seen here?
What are the 3 most common causes of Primary Hyperparathyroidism?
1. Parathyroid Adenoma = 81%

2. Parathyroid Hyperplasia = 15%

3. Parathyroid Carcinoma = 6%
What are the lab findings associated with Primary Hyperparathyroidism?
1. increased PTH
2. increased Ca+ = hypercalcemia + hypercalciuria
3. decreased serum Phosphorus
4. increased serum Alkaline Phosphatase
Parathyroid Adenoma
What is seen here?
Oxyphil cell Parathyroid Adenoma
-normal rim of parathyroid tissue containing fat cells is visible
What is seen here?
Chief Cell Adenoma
-absence of fat cells within adenoma
What is seen here?
Primary Parathyroid Hyperplasia
What is seen here?
Waterclear cell Parathyroid Hyperplasia
What is seen here?
What are the most common clinical causes of Hypercalcemia?
-
Microscopic changes in the Bone Marrow due to Malignant Lymphoma
-Malignant Lymphoblasts secrete PTH-like hormone (PTHrP) that signals Osteoclasts to resorb bone
What is seen here?
What are the most common neoplasms that produce PTHrP & cause Hypercalcemia
1. Lung CA = 25%
2. Breast CA = 20%
3. Squamous CA of Head, Neck, Esophagus, Cervix = 19%
4. Malignant Lymphoma = 14%
5. Renal Cell CA = 8%
Describe the metabolic process of Vitamin D
-
Secondary Hyperparathyroidism
-diffusely enlarge & hyperplastic parathyroids
What is seen here?
Diffuse Chief Cell Hyperplasia due to Sedoncary Hyperparathyroidism
What is seen here?
Osteoclasts resorbing bone in Secondary Hyperparathyroidism
What is seen here?
Define Secondary Hyperparathyroidism

What is the most common cause?
Compensatory Parathyroid Hyperplasia in response to decreased concentration of serum Ca+

Chronic Renal Failure = kidney doesn't convert Vitamin D into its active form -> 1, 25-(OH)2D3
What are the most common causes of Secondary Hyperparathyroidism?
1. Chronic renal failure = conversion of Vitamin D to its optimal active form is impeded -> decreased intestinal absorption of Ca+
2. Vitamin D deficiency
3. Malabsorption
What are the causes of Hypoparathyroidism?
1. accidental surgical excision (usually during Thyroid surgery)
2. developmental absence of Parathyroids
3. Absence of Thymus & Parathyroids = DiGeorge Syndrome
4. Autoimmune hypoparathyroidism
5. Pseudohypoparathyroidism
What are the clinical features of Hypoparathyroidism?
1. Hypocalcemia
2. Neuromuscular excitability & tetany
-Chvostek's sign = tap facial nerve -> contraction of facial muscles
-Trousseau's sign = occlusion of brachial artery with BP cuff -> carpal spasm
3. Psychiatric disturbances
4. Cardiac conduction defects
5. Cataracts develop due to calcifications of the lenses
Pseudohypoparathyroidism
-PTH receptors in Bone & Kidney are insensitive to PTH
What is the cause of Short stature, short neck, & short fingers in this boy?