Hyperthyroidism

Question 1

Signs and Symptoms

Answer 1

INC BMR (more Na-K) and INC SYMP NS (more beta rec)

• Adrenergic - anxiety, tremor, tachycardia, perspiration, oily skin, wide pulse pressure, hyper-defecation, lid retraction, hyper-reflexia
• Metabolic - heat intolerance, wt loss despite appetite, fever
• Misc - myopathy, loss of period, psychosis

Question 2

Diagnosis

Answer 2

• Labs - dec free T4 and low or undetectable TSH
• Then determine cause - 123 radioactive iodine uptake and scan
  • Scans 4 hrs and 24 hrs after ingestion
  • Normal = 5-15% @ 4 hrs and 10-30% @ 24 hrs
  • Inc uptake = hyperfunction v. dec uptake = thyroid destruction or exogenous thyroid hormone administration

Question 3

Differential Based on Scan

Answer 3

• Normal/Elevated RAI Uptake
  
  • Graves Disease
  • Toxic adenoma or Toxic multi-nodular goiter
  • TSH-prod pituitary adenoma - RARE
• Low RAI Uptake
  
  • Subacute (de Quervain’s) thyroiditis
  • Painless thyroiditis
  • Acute thyroiditis
  • Thyrotoxicosis factitia
  • Amiodarone-induced thyroiditis
  • Ectopic production - very rare (ex - struma ovarii)
  • Iodine use - contrast –> Jod-Basedow effect (self-limiting so rarely treat)

Question 4

Graves Disease

Answer 4

• Women > men
• Thyrotropin receptor antibodies stimulate TSH receptor –> inc thyroid hormone production (TSI and TBII)
• Leads to inc size of gland (diffuse goiter +/- audible thyroid bruit)
• Gross - dark red and glistening
• Histo - hyperplastic follicles, papillary infoldings, scant colloid (scalloped)
  
  • Using up all the colloid store
  • Follicles cramped
  • “diffuse papillary hyperplasia
• Also TSH receptors on orbital fibroblasts and shins; when antibody binds these they release more glycosaminoglycans –> exopthalmos and pretibial myxedema (dough-like)
• Tx -
• 1 - treat symptoms w/ beta blockers or Ca channel blockers
• 2- management - anti-thyroid drugs, radioactive iodine or thyroidectomy

Question 5

Toxic Adenoma or Toxic Multi-nodular Goiter

Answer 5

• Single or multiple areas of focal inc in uptake (“hot nodules”)
• Often seen later in life and more mild symptoms than Graves
• Histo - follicles of diff sizes; may be degenerating (macrophages, hemosiderin deposits from bleeding, cystic fluid)
• Cyto - normal cells; may see macrophages and old blood; lots of colloid
• Tx - no ATDs; would rather get rid of nodules (RAI in high doses or surgery)

Question 6

Subacute (de Quervain’s) thyroiditis

Answer 6

Thyroiditis = inflammation of gland –> release of stored hormone

• May be after URI or other viral illness; so fever, sweats, malaise (may have inc ESR)
• Very PAINFUL and enlarged gland
• Usually self-limiting; rarely progresses to hypothyroid

Question 7

Thyrotoxicosis Factitia

Answer 7

• Ingestion of excessive thyroid hormone (may be accidental use of hormone replacement drugs or in wt loss supplements)
• Labs - low thyroglobulin (v. thyroiditis where thyroglobulin is released along w/ thyroid hormone)

Question 8

Amiodarone Induced Thyroiditis (2 types)

Answer 8

• Type I AIT - iodine induced; diffuse goiter on US; treat w/ ATDs
• Type II AIT - destructive; amiodarone itself is toxic to thyrocytes –> thyroiditis and release of stores; dec doppler on US; treat w/ GCs but typically resolves w/o switching drug
• Check thyroid labs b/f starting drug

Question 9

Thyroid Storm + How to Treat

Answer 9

• emergency
• Triad - confusion, fever, cardio collapse
• Labs may be less severe than expected
• Usually in someone w/ underlying hyperthyroidism (Graves) + acute illness
• Tx - ATDS (specifically PTU) and supportive care (beta blockers)

Question 10

Painless Thyroiditis

Answer 10

• Most commonly 2-12 mo postpartum (when immune system inc again)
• Inc risk if prior episode or inc thyroid antibodies
• 25% persist –> classic autoimmune attack –> hypothyroid
• Tx - not ATDs b/c stores released NOT in production; treat symptoms w/ beta blockers, NSAIDs or GCs for pain
• Monitor - should resolve in 6-8 wks; if becomes permanent hypothyroid give levothyroxine

Question 11

Anti-Thyroid Drugs

Answer 11

• MAO: inhibit thyroid peroxidase enzyme in thyroid hormone prod in follicle
• T4 will dec first while TSH may still be suppressed for 3 mo
• Methimazole > PTU b/c hepatic toxicity
• PTU mainly used in 1st trimester and thyroid storm

Question 12

RAI as Tx

Answer 12

• Destroys overactive tissue; higher energy and higher dose than that used in diagnostics
• Must have low iodine diet and no ATDs to make sure RAI is taken up
• About 8 wks to see results
• May have post-ablative hypothyroidism 2-6 mo after; give levothyroxine
• Do not use if pregnant or plan to be pregnant in next 6 mo