Multinodular Goiter Flashcards
Enlarged thyroid gland
Multiple nodules
Disordered growth of thyroid cells
Gradual development of fibrosis
Multinodular Goiter
Patient is euthyroid
Enlarged thyroid gland with multiple nodules
Nontoxic MNG
Patient is thyrotoxic
1 or more nodules producing thyroid hormone INDEPENDENT of TSH regulation
Toxic MNG
Most common MNG
Nontoxic MNG
Histologic characteristic of MNG
Disordered growth of thyroid cells
Gradual development of fibrosis
MNG epidemiology
Prevalance
Sex
Age
Environment
12% adults
W>M
Increases with age
More common in iodine-DEFICIENT regions but also occur in iodine sufficiency
Risk factors for MNG
Iodine deficiency
Radiation exposure
Recent exposure to iodine from contrast dyes or other sources may precipitare or exacerbate thyrotoxicosis in toxic MNG
Pathogenesis of MNG
genetic
autoimmune
environmental
multifactorial
Major difference between toxic and nontoxic MNG is
autonomous production of excess thyroid hormone in the toxic MNG
when toxic MNG develops, it evolves from nontoxic MNG as natural history
Stages of nodular transformation of thyroid
Goitrogenic stimuli (iodine deficiency, autoimmunity, or nutritional goitrogens) cause diffuse thyroid hyperplasia
Non toxic MNG signs and symptoms
Most are asymptomatic.
Discovered 3 ways:
Goiter with multiple nodules
Incidental finding on CT (substernal goiter)
Enlargement in neck noted by patient
Compressive symptoms in large MNG
Dysphagia (rare)
Plethora venous congestion
Horner’s syndrome
In large goiters obstructing venous return within thoracic aperture
Facial congestion and external jugular vein obstruction when arms are raised above the head
Pemberton’s sign
Signs and symptoms may suggest cancer
Pain (hemorrhage into nodule) Hoarseness (laryngeal nerve involvement) Stridor Respiratory distress (tracheal compression) Tracheomalacia
PE of MNG
Thyroid architecture is often distorted with multiple nodules of varying size
Substernal goiters nonpalpable
PE underestimates the goiter size
Laboratory that distinguishes nontoxic MNG from toxic MNG
TSH
Imaging is indicated for MNG if
Verify hyperfunctioning nodules in a patient with MNG with concomitant clinical/laboratort evidence of hyperthyroidism
Evaluate degree of obstruction in large MNG
FNA for MNG is recommended
Dominant or enlarging nodule with MNG
Nonfunctioning (COLD) nodules >/= 1.5 cm in diameter
Nodules found to have microcalcifications
Complex architecture on ultrasonography
FNA should not be used on
Autonomous HOT/warm nodules
Thyroid function test if nontoxic MNG
Normal TSH
Thyroid function test if toxic MNG
TSH level is low
Normal or minimally increased FT4
CT or MRI of the chest are indicated only when
Evaluating goiter anatomy
Substernal extension
Extent of tracheal compression
Airway compromise indicates compression of tracheal diameter by how
70%
Iodinated contrast agents should be administered cautiously to persons with
Low TSH
may precipitate underlying hyperthyroidism
consider pretreatment with antithyroid drug before contrast imaging
Thyroid scintigraphy (iodine or technetium) should be limited to MNG patients with
low TSH
to verify clinical diagnosis of toxic MNG
UTZ in MNG is useful for
Accurate monitoring of nodule size
Guiding FNA biopsy of suspicious nodules
Barium swallow is indicated in MNG
To assess whether esophageal compression causes dysphagia
FNA biopsy in MNG should be considered for
A dominant nodule >1-1.5cm diameter Enlarging nodule with MNG Nodules with microcalcifications Hypoechogenecity Increased vascularity Complex architecture
Nontoxic MNG treatment
Observation if euthyroid in smal nontoxic MNG
Treatment for nontoxic MNG is indicated if
Obstructive complication
Large or progressively growing goiter
Cosmetic concerns
Forms of therapy for nontoxic MNG
Total thyroidectomy
To dec size
Radioiodine 132I
Levothyroxine
Treatment of toxic MNG is indicated
for all patients
3 forms
Total thyroidectomy
Radioiodine treatment
Antithyroid drug therapy
Provides most effective and rapid reduction in goiter size of all available therapies
Thyroidectomy
Disadvantage
Surgical risk in elderly person with cardiopulmonary disease
Surgical complications
Post-surgical HYPOthyroidism
Gradual reduction in goiter size
Safe, outpatient
Can achieve 40-50% reduction of goiter size but patient may have
Transient elevations of thyroid hormone levels within first 2 weeks after therapy
Hypothyroidism may develop
Radioiodine therapy
Started at low dose since many MNG contain autonomous regions
Avoid excessive TSH supression
Low efficacy
Regrowth after discontinuation of therapy
Levothyroxine supression
Levothyroxine can precipitate this side effect
Subclinical HYPERTHYROIDISM
Hyperthyroidism following administration of iodine or iodide as dietary supplement or as iodinated contrast for medical imaging
Jod-Basedow effect
Autoregulatory phenomenon whereby a large amount of ingested iodine acutely inhibits thyroid hormone synthesis (organification) as well as release within the follicular cells irrespective of the serum level of thyroid-stimulating hormone TSH
Wolf-Chaikoff Phenomenon
Hypo
Toxic MNG Treatment
B blockers
Radioiodine therapy (for areas of autonomy and dec the mass of the goiter)
Thyroidectomy
Antithyroid drugs (euthyroid in 4-6 weeks)
Disadvantage of treating toxic MNG with antithyroid drugs alone
Therapy is lifelong because hyperthyroidism in toxic MNG does not remit spontaneously
May increase size of goiter
