Path Flashcards
“Is the pt unable to make adequate amounts of this hormone?”
What test are we likely to perform?
Stimulation test
-Pt receives or does something that should raise levels of the hormone. If response is not adequate, dx is made.
“Is this pt unable to limit production of this hormone to what is appropriate?”
What test are we likely to perform?
Suppression test
-Pt receives or does something that should lower levels of the hormone. If response is not adequate, dx is made.
Thyroxine (T4) and tri-iodothyronine (T3) are produced in the thyroid gland.
What hormone (and from where) stimulates their production and secretion?
Thyroid stimulating hormone (TSH, thyrotropin) from the anterior pituitary
TSH production and secretion is stimulated by what (and from where)?
TSH releasing hormone (TRH) from the brain
Low T4 confirms:
HYPOthyroidism
Pts who are HYPOthyroid from thyroid dz will have high TSH. Why?
Loss of negative feedback on the pituitary
Pts who are HYPERthyroid from thyroid dz will have low TSH. Why?
Strong negative feedback on pituitary
Low T4, high TSH:
Hypothyroidism
-mimics depression, mental illness
High T4, low TSH:
Hyperthyroidism
-mimics anxiety, mental illness
Labs for 2° hypothyroidism:
Cause of 2° hypothyroidism:
Low T4, low TSH.
Pituitary does not produce adequate amount of TSH.
Labs for 2° hyperthyroidism:
Cause of 2° hyperthyroidism:
High T4, high TSH.
Overactive pituitary OR a tumor elsewhere producing excess TSH.
Anti-thyroid peroxidase Abs (anti-TPO) target an:
Iodine oxidizer
Anti-thyroglobulin Abs target the:
Colloidal storage form of thyroid hormone
Anti-TSH receptor Abs (anti-TR, “TRAbs”) are often stimulatory and cause:
Hyperthyroidism
Cortisol from the adrenal cortex is the body’s principal glucocorticoid.
Excess cortisol produces what syndrome?
Cushing’s
Adrenal or pituitary dz with HYPOadrenocorticism:
Addison’s
- Cannot stimulate cortisol production
- Mimics depression or anorexia nervosa
Adrenal or pituitary dz with HYPERadrenocorticism:
Cushing’s
- Cannot suppress cortisol production
- Mimics mental illness and other common problems
Cortisol production by the adrenal cortex is stimulated by:
ACTH
A morning serum cortisol > __ ug/dL or a morning salivary cortisol > __ ug/mL basically excludes adrenal insufficiency.
What test would you perform?
Serum cortisol > 18 ug/dL
Salivary cortisol > 5.8 ug/mL
ACTH stimulation test.
What is expected in an ACTH stimulation test in primary adrenal cortical insufficiency (due to dz of the gland itself)?
Cortisol levels won’t rise despite ACTH administration.
Auto-Abs detected in autoimmune adrenalitis:
Anti-21-hydroxylase Abs
Plasma ACTH LOW
Aldosterone LOW
Renin HIGH
Dx:
Primary adrenal insufficiency
adrenal gland problem
Plasma ACTH LOW
Aldosterone NORMAL
Renin NORMAL
Dx:
Secondary adrenal insufficiency
pituitary problem
In suspected hyperadrenocorticism, screen with:
24 hour urinary cortisol
Cushing’s pts have > 3x the upper limit of ref range
