HPA Flashcards
What are the components of the HPA axis?
-Hypothalamus: releases hormones to the pituitary
-Pituitary
-Target Tissue: Directly stimulated to cause physiologic function or release a hormone
Anterior Pituitary
-Adenohypophysis
-Produce tropic hormones
-Hypothalamus release hormones in the Anterior Pituitary and the Anterior Pituitary release now hormones to target tissue through circulation.
Posterior Pituitary
-Neurohypophysis
-Stores and secretes hormones produced by the hypothalamus
-Doesn’t produce new hormones.
Which Hypothalamic hormones have inhibitory effects on the pituitary?
-Dopamine inhibits Prolactin
-Somatostatin inhibits TSH, GH, prolactin
Long-looped negative feedback
Third level hormone (released by target gland) exerts effect on hypothalamus (indirect) or pituitary gland (direct).
Short-loop negative feedback
Pituitary hormone exert effect on hypothalamus.
What happens to the HPA axis in a pathological process?
There is going to be hyperfunction or hypofunction of hormones and would not be able to recognize negative feedback back.
What is Paraneoplastic Syndrome?
When there is an overproduction (hyperfunction) of hormones in the wrong tissue.
Determine the origin of primary, secondary, and tertiary disorders of HPA.
-Primary disorder originate in the target gland
-Secondary disorder originate in the pituitary gland
-Tertiary disorder originate in the hypothalamus.
Pituitary Adenoma (Tumor)
-Most common cause of HPA dysfunction
-Microadenomas do not cause serious symptoms
One of the following may occur:
-Hypopituitarism due to mass effect (Creates pressure in the pituitary)
-Hyperpituitarism: tumor secreates hormones
Hyperprolactinemia
Caused by Prolactin-secreting adenomas, hypothyroidism, and Drug-Induced (Dopamine antagonist or 1st generation antipsychotic)
Symptoms are menstruate problems and sexual dysfunction.
Adrenal Insufficiency (Low cortisol: <18mcg/dL)
Primary (Addison Disease):
-Caused by Drug use, tuberculosis or autoimmune)
-Elevated ACTH
Secondary (Adrenal Crisis):
-Due to rapid withdrawal of exogenous corticosteroid use (turns off the HPA axis)
-Normal to low ACTH
What effect will low mineralocorticoids (aldosterone) have on sodium and potassium status?
It will result in excessive sodium and insufficient potassium excretion in the urine which leads to hyperkalemia, hyponatremia, hypovolemia, and hyperteninemia.
Hypercortisolism (Cushing syndrome)
Exogenous (latrogenic):
-Due to excess glucocorticoids or progestins
Endogenous (More complex see other flashcard)
Endogenous Cushing Syndrome
ACTH dependent (High ACTH):
-Pituitary Adenomas (Cushing disease)
-Ectopic tumors (Pancreas, Thyroid and lungs)
ACTH independent (Low ACTH):
-Adrenal adenomas and carcinomas
