Lecture 57 "Thyroid Gland"
Terms
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- relative T/S (thyroid/serum) ratio in the presence of TSH
-
T/S ratio is high due to iodide trapping:
- TSH increases the activity of the Na/I cotransporter located on the basolateral membrane of the thyroid follicular cell - peripheral deiodinases are located in (2)
-
liver
kidney - ____ is the major thryoid hormone secreted by the thyroid gland
- T4
-
T4 vs. T3
*% bound
*biologic potency (activity)
*% oral absorption -
T4
*% bound: 99.96%
*biologic potency (activity): 1 (more T4 bound than T3)
*% oral absorption: 75-90%
T3
*% bound: 99.6%
*biologic potency (activity): 4 (because less T3 is bound than T4)
*% oral absorption: 95% - circulating T4 & T3 is bound to
- thyroxin binding globulin (TBG)
- thyroid hormones induces the transcription and translation of (5)
-
Na/K pump
gluconeogenic enzymes
respiratory enzymes
myosin heavy chain
beta adreneric receptors -
hypothyroidism:
*BMR
*gluconeogenesis
*glycogenolysis
*serum [glucose]
*protein synthesis
*protein proteolysis
*lipogenesis
*lipolysis
*serum [cholesterol]
*thermogenesis
*serum [catecholami -
*BMR: decreased
*gluconeogenesis: decreased
*glycogenolysis: decreased
*serum [glucose]: normal
*protein synthesis: decreased
*protein proteolysis: decreased
*lipogenesis: decreased
*lipolysis: decreased
*serum [cholesterol]: elevated (less readily metabolized)
*thermogenesis: decreased
*serum [catecholamines]: normal
*bowel function: decreased (constipation) -
hyperthyroidism
*BMR
*gluconeogenesis
*glycogenolysis
*serum [glucose]
*protein synthesis
*protein proteolysis
*lipogenesis
*lipolysis
*serum [cholesterol]
*thermogenesis
*serum [catecholami -
*BMR: increased
*gluconeogenesis: increased
*glycogenolysis: increased
*serum [glucose]: normal
*protein synthesis: increased
*protein proteolysis: increased (leads to muscle wasting)
*lipogenesis: increased
*lipolysis: increased
*serum [cholesterol]: decreased (increased metabolism)
*thermogenesis: increased
*serum [catecholamines]: normal (however, increased sensitivity to catecholamines due in increased expression of beta adrenergic receptors)
*bowel function: increased (diahrrea) - TSH release is inhibited by (2)
-
somatostatin
dopamine - clinical presentation of hyperthyroidism
-
elevated BMR
tachycardia
sweating
heat-intolerance
nervousness
muscle-wasting and weakness
tremor
difficulty sleeping
changes in hair growth and skin texture
toxic goiter (enlarged thyroid gland)
exophthalmos
localized mucopolysaccharide deposition (under eyes)
eyelid retraction
thyroid storm - lab values for a pt. with hyperthyroidism
-
presence of thyroid-stimulating immunoglobulins
decreased TSH (T4 & T3 negative feedback)
increases thyroid hormone - clinical presentation of hypothyroidism
-
decreased BMR
cold-intolerance
lethargy
headache
skin changes
constipation
non-toxic goiter (enlarged thyroid gland due to increased colloid deposition - colloid/TG lacks associated TH)
general mucopolysaccharide deposition (face)
myxedema coma - lab values for a pt. with hypothyroidism
-
anti-thyroid antibodies
increased TSH (no T4 & T3 negative feedback)
decreased TH