2/14 Thyroid AE_Pathophys Flashcards
thyroid anlage
thickened foregut endoderm
site where thyroid devpt begins
thyroid devptal pathology
most congenital hypothyroidism linked to abnl thyroid gland devpt
- maldescent → lingual thyroid, retrosternal thyroid
- thyroglossal duct cysts
hum over active thyroid
why?
incr venous blood flow from hyperplastic/hypertrophic gland
euthyroid
hypothyroid
hypertyroid
thyrotoxicosis
subclinical
euthyroid : normal thyroid hormone action
hypothyroid : underactive thyroid gland, clinical evidence of deficient thyroid hormone action
hyperthyroid : overactive thyroid gland & clinical evidence of excess thyroid hormone action
thyrotoxicosis : clinical evidence of excess thyroid hormone action
subclinical : only lab evidence of hormone excess/def
fx of thyroid hormone
controls metabolic rate
congenital hypothyroidism
causes
clnical findings
causes
- thyroid gland dysgenesis
- inborn errors of TH synthesis
- TSH-receptor blocking ab from mom
clinical findings
- jaundice
- feeding troubles
- enlarged tongue
- umbilical hernia
- delayed bone maturation
majority identified by newborn blood screening!
endemic cretinism
hypothyroidism → issues with brain devpt
- mental retardation (MBP)
- movement disorders (PCP2)
goiter
enlarged thyroid
most common cause: IODINE DEFICIENCY
hypothyroidism
signs and sx (juvenile vs adult)
juvenile
- mental retardation, learning disabilities
- short stature
adult
- CNS : delayed deep tendon reflexes, mental slowness
- CV: bradycardia, weakness
- periorbital and peripheral edema
- dry coarse hair, orange skin (keratin), decr BMR, cold intolerance, weight gain
- repro: menorrhagia
- GI: constipation
classification of hypothyroidism
x3 and causes
-
PRIMARY hypothyroidism : TSH high
- Hashimoto’s aka chronic lymphocytic thyroiditis (95% cases in US)
- drug induced (Li, I)
- TH synthesis defects (ex. thyroperoxidase issues)
- lingual thyroid (devpt defect)
- iodine def
- infiltrative disease (amyloid, fibrous replacement)
-
CENTRAL hypothyroidism (TSH nl, low)
- pituitary or hypothalamic disease (rad, tumor, infiltrative)
-
TRANSIENT hypothyroidism (TSH variable → can progress to permanent)
- postpartum or silent thyroiditis (painless, related to lymphocytic)
- after preg, woman has a flareup of autoimmunity
- subacute thyroiditis (deQuervain’s or painful thyroiditis, viral in origin)
- postpartum or silent thyroiditis (painless, related to lymphocytic)
primary hypothyroidism
LACK OF HORMONE FOR NEGATIVE FEEDBACK
may or may not present with goiter
Hashimoto’s thyroiditis
aka
chronic lymphocytic thyroiditis
most common cause of permanent hypothyroidism
autoimmune disase assoc with DR5 and antiTPO antibodies
- high prevalence: women, Japanese (maybe high I diet)
- “Hashitoxicosis”: early thyrotoxic phase due to follicular rupture (rare presentation)
- end-stage? atrophic thyroiditis
- assoc with incr risk of thyroid lymphoma
central hypothyroidism
low hormone levels due to INADEQUATE CENTRAL STIMULATION
normal or small thyroid gland
transient hypothyroidism
most common causes of transient hypothyroidism:
- subacute (painful) thyroiditis
- referred jaw pain, viral in origin, confused with pharyngitis
- postpartum (painless) thyroiditis
- can recur with subsequent pregs or progress to Hashimoto
can result in a triphasic response (destruction, repair, normal)
- destruction: TSH suppressed
- no radioactive update during destructive phase
- repair: TSH high
- repairED: TSH normal
thyrotoxicosis
signs/sx
juvenile vs adult
prenatal/juvenile
- cranial synostosis (premature fusion of cranial sutures)
adult
- tachycardia, afib, dyspnea, palps/angina
- inability to concentrate, active CTRs, tremor
- thyroid bruit, eye, skin complaints (Graves disease)
- pain in neck or jaw → subacute thyroiditis
- velvety, moist skin, incr BMR, wt loss
- oligomenorrhea (light/infreq periods)
- diarrhea
- osteoporosis
effect of thyroid hormone on basal metabolism
thyroid hormone increases cell membrane permeability to Na and K → incr in Na/K ATPase activity
- making ATP is not totally efficient → some energy is released as heat
*
classification of thyrotoxicosis
- HYPERTHYROIDISM (TSH undetectable)
- Graves’ disease (most common, 60% cases)
- toxic adenoma (solitary overactive nodule)
- toxic multinodular goiter (TMNG common, many overactive nodules aka Plummer’s disease)
- THYROID DESTRUCTION (TSH variable)
- subacute or painful thyroiditis (common)
- postpartum thyroiditis (common)
- Hashitoxicosis : transient thyrotoxicosis phase of Hashimoto’s thyroiditis
- atypical causes (rare)
thyrotoxicosis
vs
hyperthyroidism
thyrotoxicosis: increased thyroid hormone and evidence of TH excess no matter what the cause
Graves Disease
triad
most common cause of thyrotoxicosis
- goiter
- opthalmopathy
- dermopathy
- aka pretibial myxedema
incr activity of T helpers → causes B cells to become active → production of oligoclonal TSH receptor abs
- abs bind to TSH receptor and activate it (as if TSH were bound) →→→ growth and overactivity
prevalence: 2% females, 0.2% males
risk factors: genetics, smoking, postpartum pd
summary
