RE Thyroid
Terms
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embryological origin of thyroid
(and congenital disorder) -
between 2nd & 3rd pharyngeal pouches
migrates
thyroglossal cyst= remnant of thyroid at base of tongue
pyramidal lobe=remnant of thyroid duct - histology of thyroid
-
columnar epis
TSH causes to grow
only cells to uptake iodine
full of colloid - colloid
-
contents of thyroid epis
thyroglobulin & tyrosein - production of thyroid hormone
-
peroxidase
-oxidize iodine
-add iodine to tyroseine (MIT then DIT)
-couple 2 DIT to make T4
deiodinase
-activates T4 to T3 (mostly in blood)
-T3 enters nucleus - thyroid hormone in circulation
-
bound to thyroid binding globulin
(albumin 15%, transthrine 10%) - factors affecting TBG
-
(thyroid binding globin)
increased
-estrogen
-(congenital excess)
decreased
-hepatic dz
-(congenital defect) - function of Thyroid hormone
-
4 B's
bone growth (synergism w/GH)
brain maturation
beta adrenergic
-(increased CO, HR, SV & Ctx)
BMR increase - regulation of TH
-
TRH (in hypothal)
-stim'd by increased glyc use, GNG, lipolysis
-stims TSH in pit
inhibited by
-feedback inhibition by T3
-ant pit decreases sensitivity to TRH
TSI stimulates TSH
(Graves Dz) - thyroid abnormalities
-
TH excess
TH defic
Thyroid nodules/Ca
TH resistance
Nonthyroidal illness - autoimmune destruction of thyroid cells
- Hashimoto's
- causes of hypothyroid
-
hashimotos (#1 cause US)
iodine def (#1 cause world)
surgery
Pituitary
congenital
cretinism - big belly, infantile, decreased growth
-
cretinism
(congenital hypothyroid) - fatigue, dry skin, hair loss, weight gain, cold intolerance
- hypothyroid
- hypothermia, bradycardia, thickened dry skin
- hypothyroid
-
hyporeflexia
(myxedema coma if severe) - hypothyroid (pathogmnemonic)
- treatment for hypothyroid
-
replacement
-porcine
-synthetic (levothyroxine, liothyronine) - TH4 replacement
-
levothyroxine
7 day t 1/2 - TH3 replacement
-
liothyronine
8 hr t 1/2 - causes of goiters
-
TSH elevation (regardless of thyroid fctn)
-iodine deficiency
-Grave's (TSI stims R)
-primary hypothyroid
-thyroid adenoma (multinodular "goiter")
-secondary hyperthyroid (TSH secreting pituitary tumor) - causes of hyperthyroid
-
Grave's (most common)
Thyroiditis
Adenoma ("hot nodule", T3)
receptor cross reactivity (HCG, molar pregnancy, HCG, LH, FSH activate beta)
TSH secreting pituitary tumor
Iatrogenic/facticious
ectopic (struma ovari makes T4) -
weight loss, increased appetite, BMR increased,
tachy, mental status, poor sleep
weak, fatigue, decreased ex tol - hyperthyroid
- mechanism of Graves
- autoimmune production of TSI (activates TSH R's)
-
pretibial edema
EOM hypertrophy -
Grave's
(hyperthyroid) - thyroid storm
-
clinical dx (don't wait for labs)
tachy, diaphoretic (sweat) - tachy, diaphoretic, cardiac, neuro thermo instability
-
thyroid storm
underlying tyroid
-MVA
-accident - drugs that block TH synthesis
-
(peroxidases)
PTU
Methimazole - diffuse toxic goiter
- Grave's
- nodular toxic goiter
- hyperthyroid (Plummer's-selective T3 secreting tumor)
- diffuse simple goiter
- iodine deficiency