Thyroid

Most commons

  • Hyperthyroid - Grave's
  • Hypothyroid - Hashimoto's
  • Cancer - papillary

Multiple endocrine neoplasia

Thyroiditis

Thyroiditis Clinical Labs Management
Hashimoto
(chronic autoimmune)
  • Mostly hypothyroid sx
  • Diffuse goiter

+ TPO antibody (thyroid peroxidase)

Variable RI uptake

  
Painless/silent
  • Variant of Hashimoto
  • Mild brief hyperthyroid sx
  • Small nontender goiter
  • Spontaneous recovery

+ TPO antibody (thyroid peroxidase)

↓ RI uptake

  
Subacute (de Quervain)
  • Postviral inflammation - follicular injury releases stored/preformed hormone
  • Fever, hyperthyroid sx
  • Painful/tender goiter
  • Self-limited hyperthyroid sx x few weeks, transient hypothyroid, then euthyroid

↑ ESR, CRP

↓ RI uptake

Supportive - NSAIDs, beta blocker

No abx - viral!
Acute
  • Bacterial (staph aureus or strep pyogenes) via thyroglossal fistula or anatomic variant
  • Painful, fever
   Abx + I&D - need to find source
       
Grave's  

anti-TSH receptor antibodies

↑ RI uptake (diffuse)

Medical - propranolol, methimazole to make euthyroid prior to surgery

XRT - RI thyroid ablation

Surgical - b/l subtotal thyroidectomy (indicated if suspicious nodule, pregnant, or pediatric)

Prednisone if ophthalmopathy (RAI can make it worse)
Toxic adenoma   ↑ RI (focal); hot nodule = no FNA needed

Anti-thyroid drugs to make euthyroid prior to surgery

Definitive - RI thyroid ablation vs surgery
Toxic multinodular goiter (Plummer's)     Surgery - lobectomy or near-total thyroidectomy

Pregnancy

    • Physiologic changes - low TSH, high total T4, normal to slightly high free T4
    • Estrogen increases thyroid binding globulin (TBG) synthesis -> increased thyroid hormone production to maintain free T4 levels
    • hCG acts like TSH -> T4 production with feedback inhibition of TSH
  • Goal is slightly hyperthyroid - hypothyroidism can cause fetal hypothyroidism and goiter

Thyroid nodule

  • Clinical evaluation, TS, US
  • Features suggestive of cancer
    • Hx: hx neck radiation, family hx, young age, M > F
    • Single nodule, cold nodule (5% cold nodules malignant; all hot nodules are benign), elevated calcitonin (medullary thyroid ca), lymphadenopathy, hard/immobile nodule
    • Sx (voice change, dysphagia/neck discomfort, rapid growth)
  • FNA if cancer risk factors/suspicious US - nodules > 1 cm, malignant concern on US, or growing, or if TSH normal/elevated
    • Benign - annual follow-up with US, no intervention
    • Malignant/indeterminant - thyroid lobectomy + frozen section
      • Follicular cancer = total thyroidectomy
  • Low TSH and no cancer concerns - 123I study
    • Hot nodule = benign; treat hyperthyroid
    • Cold nodule - 5% malignant; obtain FNA

 

Radioiodine study (123I scintiscan)

  • Normal - 5-30% uptake at 24 hrs
  • Indications for 123I scintiscan: need more data (e.g. nodule with multiple nondiagnostic FNAs) or possible hyperfunctioning adenoma (nodule with thyrotoxicosis, low TSH)
  • Papillary - 70% have 131I uptake (Hurthle only 5%, none with medullary)
Low uptake Focal Patchy Diffuse
  • Subacute/De Quervain's
  • Silent/painless thyroiditis
  • Postpartum thyroiditis
  • Surreptitious thyroid hormone abuse
  • Iodine-induced thyroiditis
  • Hyperfunctioning adenoma
  • Toxic multinodular goiter
  • Grave's disease - thyrotropin receptor autoantibodies stimulate iodine uptake and thyroid hormone synthesis

Thyroid cancer

  • Cancer is generally euthyroid
  • Check Ca after thyroidectomy to make sure parathyroids OK. If parathyroid blood supply compromised during surgery, re-implant
  • In order of incidence:
  Treatment Follow up

Papillary

  • Popular - most common
  • Psammoma bodies
  • Palpable lymph nodes - lymphatic spread
  • Positive prognosis - slow spread
  • Positive 131I uptake (70%) - compared to 5% Hurthle's none for medullary
  • Postop 131I scan for mets

< 1.5 cm, no hx rads

  • lobectomy vs. near-total vs. total thyroidectomy

> 1.5 cm, bilateral, or cervical node mets

  • Total thyroidectomy

Dissection controversial

  • Palpable lateral cervical nodes - ipsilateral modified neck dissection
  • Central lymph nodes - central neck dissection
 123I to find missed tumor, then 131I ablation

Follicular

  • Far-away mets - hematogeneous spread - more aggressive than papillary. Mets to bone
  • Favorable prognosis
  • FNA CANNOT be used for diagnosis - need formal bx to see tissue structure
  • Female (3:1 F:M)

Lobectomy

Near total vs. total thyroidectomy

Hematogeneous spread = no need for lymph node dissection

 131I scan for dx/rx

Medullary

  • a/w MEN2A/2B
  • Elevated calcitonin
  • aMyloid histology
  • Median dissection; Modified if + lateral nodes
 Total thyroidectomy AND median lymph node dissection. Modified neck dissection if + lateral cervical nodes Screen family members for MEN 2 (calcitonin)

Hurthle

  • Subtype of follicular carcinoma, slightly worse prognosis
  • Similarly cannot use FNA for diagnosis
  • Lymphatic > hematogeneous mets
  • Does not take up 131I
    

Anaplastic

  • Giant cells, spindle cells on histology

Small tumor - total thyroidectomy + XRT

compromised airway - debulk, trach

  

 

Rx for hyperthyroid

  • Propylthiouracil (PTU)
    • Inhibits thyroid peroxidase - decrease thyroidal T4/T3 production
    • Inhibits T4-5'-deiodinase - decrease extrathyroidal T3  production (quicker control)
    • Hepatotoxicity
    • However preferred in 1st trimester of pregnancy (methimazole teratogenic), then switch to methimazole in 2nd/3rd trimesters
  • Methimazole only inhibits thyroid peroxidase
    • Preferred drug as PTU has risk of severe hepatotoxicity
    • Teratogenic effects (aplasia cutis) in 1st trimester
author: last edited: Oct. 21, 2018, 11:17 a.m. | pk: 138 | unpublished