Endocrine 1 and 2 Flashcards
What are the 2 ways hormones can be transported?
- Bound to plasma proteins
2. Free in the blood
Which hormones are biologically active?
Those that are free in the blood
What are 3 general characteristics of hormones?
- They have a specific rate of secretion
- Feedback systems, either positive or negative feedback
- Affect only cells with the appropriate receptors
What are the 5 functions of the endocrine system?
- Homeostasis
- Energy metabolism
- Reproduction
- Growth and development
- Response to stress and injury
What are the 3 types of endocrine disease?
- Oversecretion or hyper function
- Undersecretion or hypo function
- Mass effect or tumors
What is mass effect?
A tumor presses on another organ altering its function
Where is the parathyroid gland located? How many are there usually? What is the range of how many there can be?
Located on the posterior part of the thyroid gland. Normally there are 4 of them but can be 1-12
The parathyroid glands are derivatives of?
The third and fourth branchial pouches
What are 3 possible ectopic locations of the parathyroid?
Intrathyroid, intrathymic, anterior mediastinum
Is the parathyroid gland encapsulated? What three things make up the gland?
Yes
Oxyphil cells, chief cells, stromal fat
Describe the appearance of a chief cell?
Polygonal cells with clear cytoplasm (glycogen), central uniform nuclei
Describe an oxyphil cell
Has acidophilic cytoplasm with abundant mitochondria
Stromal fat makes up what percentage of the gland?
30%
What controls the release of PTH?
Free or ionized calcium
How does PTH regulate calcium?
- Causes release of calcium from bone
- Decreases reabsorption of phosphate and increases calcium absorption in the kidney
- Vitamin D3 is hydroxyl and this causes reabsorption of calcium in the intestine
What is the range for serum calcium and free calcium?
Serum is 8-10 mg/dl
Free is 4-5.6 mg/dl
What is the normal range for PTH?
10-65 nanomoles/L
What are the 2 general causes of hypercalcemia?
Raised PTH or lowered PTH
Raised PTH is due to hyperparathyroidism, what are the usual causes of PRIMARY hyperparathyroidism?
Almost always an adenoma but can also be from hyperplasia, (carcinoma 1% of the time)
Does increased PTH always lead to hypercalcemia?
No calcium can be high, low, or normal depending on RENAL FUNCTION
What causes SECONDARY hyperparathyroidism?
Increase in PTH secondary to HYPOcalcemia and HYPERphosphatemia of chronic renal failure
What is TERTIARY hyperparathyroidism?
Autonomous parathyroid hyper function in those with secondary hyperparathyroidism
What can cause decreased PTH?
Malignancy (anywhere like small cell carcinoma of the lung) Vitamin D toxicity Immobilization Thiazide diuretics Granulomatous disease like sarcoidosis
Most cases of hyperparathyroidism are?
Asympomatic (see chart for possible symptoms)
What two effects does excess PTH have on bone?
Osteoporosis and ostelitis fibrosa cystica (brown tumor)
In ostelitis fibrosa cystic what cells are present in marrow?
Multinucleated giant cells, inflammatory cells, also fibrosis
What can ostelitis fibrosa cystica present as?
Cystic lesion in small bones
How can you detect how many parathyroid glands are enlarged?
Sestamibi scanning
Parathyroid adenomas occur more in men or women?
3x more often in women
How do you distinguish an adenoma from hyperplasia?
An adenoma will be sharply demarcated from the gland
Parathyroid hyperplasia typically occurs in how many glands? Does this differ from adenoma?
Typically in all four glands, adenoma is usually just in one
Why does parathyroid hyperplasia occur?
Either a sporadic thing most of the time or as part of MEN (multiple endocrine neoplasia) 2A
Parathyroid hyperplasia usually exhibits hyperplasia of which cell? What other cells are present?
Chief cells, variable oncocytes
What is the most common sign of parathyroid carcinoma?
A palpable neck mass
Carcinoma leads to?
Excessive PTH, even more than adenoma or hyperplasia, usually > 14 mg/dl serum calcium, normal is 8-10
Histologically how do you identify parathyroid carcinoma?
Should see capsular invasion and hyper plastic chief cells
What are the ABSOLUTE criteria for parathyroid carcinoma?
Vascular invasion and metastasis
What is associated with aggressive parathyroid carcinoma?
Macronuclei, more than five mitoses per 50 high power fields, and necrosis
What are the 3 types of MEN?
MEN 1 or Wermer syndrome
MEN 2A or Sipple’s syndrome
Men 2B
In wermers neoplasia will occur where?
Pituitary, parathyroid, pancreas, and carcinoids
MEN 2A or simple’s will lead to what cancer?
Medullary thyroid or c cell and pheochromocytomas
MEN 2B will lead to neuromas in…
What other cancers?
Eye, buccal, and GI mucosa
Medullar thyroid or c cell carcinoma
Pheochromocytomas
Which MEN syndromes lead to parathyroid hyperplasia?
Type 1 or wermer’s and type 2a or sipple’s
What is similar about MEN 2a and 2b?
Both can lead to pheochromocytomas and medullary thyroid or c cell carcinoma
What is the largest endocrine organs?
The thyroid
What is located in the lumen of the thyroid?
Colloid
What 2 cells are present in the thyroid?
C cells and epithelial follicular cells
What hormones are produced in the thyroid and by which cells>
T3 and T4 are produced by the epithelial follicular cells
Calcitonin is produced by the c cells
What causes the thyroid to release T3 and T4?
Thyroid stimulating hormone
What causes the release of TSH from the pituitary?
Thyroid releasing hormone from the hypothalamus
Where does thyroid tissue begin forming embryologically?
Foramen cecum
Where is the thyroid normally located?
In front of the larynx
Ectopic locations of the thyroid include?
Lingual, mediastinal, heart, anterior tongue
What is a thyroglossal duct cyst?
Persistence and dilatation of the thyroglossal duct in the midline of the neck, only a problem if infected
What lines the thyroglossal duct cyst?
Either squamous or respiratory epithelium
What is the most common cause of hypothyroidism in the US? Worldwide?
Hashimoto’s thyroiditis
Iodine deficiency
What are causes of secondary hypoparathyroidism?
Pituitary or hypothalamic failure
Levels of which hormone will be high in hypothyroidism?
TSH
What effects does hypothyroidism have on infants? Adults?
Cretinism
Myxedema or edema of the eye area
What is the most common cause of goiter in the US? The origin of this disease is?
Hashimoto thyroiditis, immune origin
What is the histologic “triad” of hashimoto thyroiditis?
- Lymphocytic infiltrate
- Lymphoid follicles with germinal centers
- Hurthle cell metaplasia of follicular epithelium
Those with hashimoto thyroiditis are at risk of?
B cell lymphoma, papillary carcinoma, Hurthle cell neoplasm
What are the 2 other names for subacute thyroiditis?
Granulomatous and De Quervain
What is the cause of subacute thyroiditis? Describe the clinical course
Viral infection
Triphasic clinical course of hyper, hypo, then normal thyroid function
Subacute thyroiditis is the most common cause of?
Painful thyroid
What cell is present in subacute thyroiditis?
Multinucleated giant cells since its an infection
In Riedel’s thyroiditis what is the most important thing you will see histologically?
Obliterating phlebitis
Why is thyrotoxicosis?
Hypermetabolic state caused by increased T3 and T4
What is the primary cause of thyrotoxicosis? Secondary?
Grave’s disease
TSH secreting pituitary adenoma
What type of thyroid nodule is more likely to be malignant?
A cold one
What is the most definitive way to diagnose thyroid cancer?
Fine needle aspiration
What is the most common malignant thyroid tumor?
Papillary carcinoma
A papillary carcinoma will be lined with?
Fibrovascular core with cuboidal, columnar cells and psammoma bodies
What is the most common thyroid neoplasm?
Follicular adenoma
How do you differentiate adenoma from well differentiated carcinoma?
Integrity of the capsule
