Flashcards in Endocrine Deck (108)
What is the most common site of ectopic thyroid tissue?
What does the thyroglossal duct become?
What if it persists?
Normally thyroglossal duct --> foramen cecum
If it persists --> thyroglossal duct cyst
(midline mass that moves with swallowing)
What adenohypophyseal hormones share a common subunit?
These all share the same alpha subunit (beta determines spec.)
What do the basophil cells secrete in the anterior pituitary?
What endocrine cell types are found in the pancreas?
Beta - Insulin
Alpha - Glucagon
Delta - Somatostatin
PP - Pancreatic polypeptide
This is the order of abundance
What tissues can take up glucose regardless of insulin status?
What are the glucose transporters and their locations?
GLUT1 (insulin-independent) --> RBC's & brain
GLUT2 (bidirectional) --> Beta cells, liver, kidney, small intestine
GLUT4 (insulin-dependent) --> Adipose tissue, skeletal muscle
What is insulin's effect on renal tubules?
Causes sodium retention
What 3 things cause release of insulin?
What 3 things inhibit it?
GH (causes insulin resistance --> increased release)
What are the steps within beta cells leading to insulin release?
Glucose enters via GLUT2
Glycolysis --> ^ATP
ATP-sensitive K+ channels close --> Depolarization
Voltage-gated Ca2+ channels open
Exocytosis of insulin granules
What pathways are responsible for the intracellular effects of insulin?
Phosphoinositide-3 kinase pathway --> GLUT4 inserted into membrane & synthesis of glycogen, lipids, proteins
RAS/MAP kinase pathway --> Cell growth, DNA synthesis
What changes occur within target tissues that cause insulin resistance?
Serine kinase phosphorylation of signaling molecules. This causes inhibition of the Phosphoinositide-3 kinase pathway so that GLUT4 cannot be inserted into the membrane.
What is the regulation of prolactin?
TRH --> +Prolactin
Dopamine --> -Prolactin
What does CRH stimulate release of?
Melanocyte-Stimulating Hormone (MSH)
What is Somatostatin's effect in the pituitary?
Decreases GH & TSH release
What are the effects of growth hormone?
Stimulates linear growth & muscle mass (IGF-1 mediated)
What can stimulate GH secretion?
How does 17-alpha-hydroxylase deficiency present?
Cortisol & androgens cannot be produced:
Males - pseudohermaphroditism (ambiguous genitalia)
Females - normal anatomy, no secondary sex characteristics
How does 21-alpha hydroxylase deficiency present?
Most common form of congenital adrenal hyperplasia
^Androgens, deficient cortisol & mineralocorticoids
Masculinization in females --> pseudohermaphroditism
How does 11-beta-hydroxylase deficiency present?
^Androgens, ^mineralocorticoids, deficient cortisol
Masculinization of females
What is seen with congenital aromatase deficiency?
Increased Testosterone and decreased Estrogen levels
Maternal hirsutism while pregnant w/ affected fetus
What are the actions of cortisol?
Decreases bone formation
Upregulates alpha1 receptors on arterioles (sensitizes)
Gluconeogenesis, lipolysis, proteolysis, inhibits fibroblasts
How can one differentiate primary adrenal insufficiency vs HPA axis dysregulation?
Metyapone inhibits 11-beta-hydroxylase --> should see compensatory rise in ACTH --> Increased cortisol precursors (urinary 17-hydroxy-corticosteroids or 11-deoxycortisol)
If ACTH^ but not the precursors --> adrenal problem
If no ACTH^ --> HP axis problem
How does cortisol affect blood pressure?
1) It upregulates Alpha1 adrenergic receptors on arterioles --> sensitizes them to catecholamines
2) It increases transcription of phenylethanolamine-N-Methyltransferase (NE-->EPI)
How does PTH stimulate osteoclastic activity?
Increases production of M-CSF & RANK-L in osteoBLASTS
How is PTH secretion regulated?
Decreased serum Ca2+ --> ^PTH
Decreased serum Mg2+ --> PTH
Very low serum Mg2+ --> Decreased PTH
Thus, if magnesium levels are very low, a patient may not respond well to Calcium supplementation (need Mg2+ as well).
What can cause hypomagnesemia?
What form of Vit. D is active?
What forms are inactive?
Active = 1,25-Cholecalciferol = Calcitriol
Inactive = 25-OH-D3 & 24,25-OH-D3
How is Vit. D acquired?
Where is Vit. D activated?
D2 is dietary, D3 is synthesized in skin
Converted to 25-OH-D3 in liver
Converted to 1,25-OH-D3 in kidney PCT