Thyroid Disorders

Table Of Contents
1 Thyroid
2 Thyroid Chart
3 Hyperthyroidism
4 Hyperthyroidism (Grave’s disease)
5 Hypothyroidism
6 Thyroid Storm
7 Thyroid Nodules
8 Thyroid disease in Pregnancy
9 Thyroid Cancer
10 Papillary Carcinoma
11 Follicular Carcinoma
12 Medullary Thyroid Carcinoma
13 Anaplastic Carcinoma

Thyroid

  • secrete hormones which control metabolic pathways and numerous physiological functions 2 hormones produced:
    • 1. Thyroxine (T4)- Thyroid produces 100mcg of thyroxine daily (converted to T3 in periphery like a prodrug) (half life of 7 days)
    • 2.Triiodothyronine (T3)- Body produces 30mcg daily
  • 15-20% from thyroid, 75-80% from conversion of T4 in the body (half life of 24 hours)
  • T4 converted to T3 intracellular, with T3 being the “active” form of thyroid hormone

Thyroid Chart

Hyperthyroidism

  • Types: Increase thyroid production
    • MC: Graves disease
    • Thyroiditis
    • Toxic adenoma
    • Toxic multinodular goiter
    • Thyrotoxicosis: clinical syndrome due to elevated thyroid hormones
 

Hyperthyroidism (Grave’s disease)

  • RIsk Factors:
    • 20-60s (20-40 graves)
    • F>M
    • Caucasians & Hispanic>AA
    • family history
  • Presentation:
    • -Nervousness
    • -Anxiety
    • -Palpitations
    • -Fatigue
    • -Emotionally labile
    • -Menstrual disturbances
    • -Heat intolerance
    • -Weight loss & increase appetite
    • -Diarrhea

    • -Warm, smooth, moist skin
    • -Exophthalmos
    • -Tachycardia
    • -Atrial Fibrillation
    • -Pretibial myxedema
    • -Unusually fine hair
    • -Retraction of the eyelids
    • -Gynecomastia
  • Tests:
    • Low TSH serum concentration
    • TSH < 0.5 mIU/L
    • Elevated FT3 and FT4
    • Elevated radioactive iodine uptake (RAIU)
    • Thyroid-stimulating antibodies (TSAbs)
  • Pharmacologic:

 

    • Anti-thyroid meds
      • -PTU (propylthiouracil)
      • -Methimazole (MMI)
    • BB (for symptoms) propranolol
    • Radioactive iodine 131
    • Surgery
  •  
  • Non Pharmacologic Treatment: 
    • Consider surgery if:
      • Large thyroid gland
      • Severe ophthalmopathy (tissues and muscles behind the eyes swell)
      • Lack of remission on antithyroid drug
      • Preparation for thyroidectomy
      • Antithyroid drug for 6-8 weeks
      • Addition of iodides for 10-14 days
      • Propranolol (post surgery as well)

Hypothyroidism

  • Types: 
    • Clinical (overt) primary hypothyroidism: High TSH, Low T4, you can treat it
    • Subclinical primary hypothyroidism: High TSH, Normal T4, maybe it has complication
    • Central hypothyroidism: Low T4, low/normal TSH
  • Presentation:
    • Classic signs/symptoms
    • Low metabolism
    • Fatigue
    • Weight gain
    • Unique sign
    • Goiter
  • Treatment:
    • Levothyroxine (Synthetic T4): AM 1hr b/f food, empty tummy, or bedtime (2hr post)
      • Dosage:
        • Levothyroxine dosing Age < 60: 1.6 mcg/kg/day by mouth (PO)
        • Levothyroxine dosing Age ≥ 60: 25 to 50 mcg PO once daily
        • Levothyroxine dosing Known or suspected CVD: 12.5 to 25 mcg PO once daily
      • Side Effects: 
        • Worsening of glycemic control in patients with diabetes mellitus (DM)
        • Decreased bone mineral density
    • Liothyronine (Synthetic T3)
    • Levothyroxine/liothyronine combination
    • When to treat Subclinical hypothyroidism: 
      • TSH > 10 mIU/L or TPO antibodies are detected
      • TSH 2.5 to 10 mIU/L for women
  • Goal of treatment for Hypothyroidism: 
    • Resolve symptoms
    • Normalize TSH
    • Avoid over-treatment
  • Adverse Effects of therapeutic overdose:
    • Arrhythmias
    • Dyspnea
    • Headache
    • weight loss
    • Rash
    • Muscle spasms
    • Menstrual irregularities
  • Monitor of Treatment:
    • 4-6 wks until stable (TSH and T4)
    • Make patient euthyroid
    • Adjust maintenance dose with increase or decrease in weight, prego, etc

Thyroid Storm

  • Def: 
    • Life-threatening medical emergency characterized by untreated hyperthyroidism that can be precipitated by infection, trauma etc.
  • Causes: 
    • Infection
    • Trauma
    • Surgery
  • Presentation:
    • Fever (>103◦F)
    • Tachycardia
    • Tachypnea
    • Coma
    • Psychosis 
    • Sweating/fever
    • AMS
    • Shock/high output HF
  • Treatment:
    • PTU, Beta blockers, steroid (decrease T4-T3 conversion)
    • Iodine once stable 

Thyroid Nodules

  • Etiology:
    • 90% begnin (W>M), most euthyroid
    • Can become malignant if: 
      • head/neck radiation
      • FHx thyroid cancer
      • malignancy hx
      • >1cm
      • Non mobile /firm
      • Elevated Calcitonin
      • Cold Nodule 
  • Evaluation:
    • If TSH decreased
      • –> hyperfxn-- lights up–> rarely cause cancer
      • -Cold/hypofxn should get fine needle aspiration
    • If TSH increased/normal
      • -hypofxn
      • -Cold–>FNA
      • monitor yearly
  • Fine Needle Aspirations:
    • nodules should get FNA if <1cm and:
    • irregular margins
    • microcalcifications
    • taller than wide (Oval)
    • Rim calcifications with extrusion of soft tissue
  • FNA Results:
    • Non diagnostic or unsatisfactory: repeat FNA
    • Benign: clinical follow up with palpation or US every 6-18 m
    • Atypia of undetermined significance (AUS): clinical correlation and repeat FNA
    • Suspicious for follicular neoplasm (SFN) or follicular neoplasm (FN): surgical lobectomy
    • Suspicious for malignancy (SFM): lobectomy or near total thyroidectomy
    • Malignant: near total thyroidectomy

Thyroid disease in Pregnancy

  • MOA:
    • hCG-> stimulates TSH-R
    • Placenta increase thyroid metabolism
  • Hypothyroidism:
    • –> levothyroxine (need higher dose b/c estrogen increases thyroxine binding globulin (TBG)
    • if not treated by 2nd trimester-> developmental delay
    • increase preeclampsia risk
  • Hyperthyroidism:
    • mild may occur during 1st 4 months with hCG increase
    • untreated–> heart failure, preterm, preeclampsia
    • PTU until 16 weeks then switch to MTZ

Thyroid Cancer

  • Presentation: 
    • hard/firm nontender nodule
    • Fixed
    • painless
    • Hoarsness
    • neckpain
    • enlarged lymph nodes
  • Risk Factor: 
    • Radiation
    • FHx of goiter
    • genetic syndrome (MEN)
  • Treatment: 
    • Surgery- recurrent laryngeal nerve injury, hypoparathyroidism
    • Radioiodine 
    • TSH suppression- Levothyroxine
    • Chemo/radiation
  • Prognosis:
    • Normally survive
    • increase mortality: men, older, mets, fast growing

Papillary Carcinoma

  • MC type of thyroid carcinoma (80%), least aggressive
  • h/o radiation
  • Slow growing from follicular cells–> invades surrounding structures and cervical nodes 
  • TSH sensitive
  • 30-40 yr

Follicular Carcinoma

  • 2nd MC, slightly more aggressive
  • Grows from follicular cells
  • Spreads through invasion, lymph, or blood to bone, brain, or lung
  • 30-50s 
  • TSH sensitive
  • More chance of mets

Medullary Thyroid Carcinoma

  • Associated with MEN 2A and MEN 2B (pheochromocytoma)
  • Familial syndromes
  • sporadic

Anaplastic Carcinoma

  • Presentation:
    • Most aggressive/worst prognosis (within 1 yr)
    • 50-60s
    • Rapid growing
    • hoarseness
    • vocal cord paralysis
    • cervical mets
  • Treatment:
    • thyroidectomy with neck dissection
    • Tracheotomy
    • Chemo/XRT