Colloid Goitre Causes
Colloid goitre is primarily caused by iodine deficiency, which affects 500-600 million people worldwide and greatly enhances the incidence of multinodular goiter. 1
Primary Etiological Factors
Iodine Deficiency
- Iodine deficiency is the dominant cause globally, with severe deficiency causing goiter and hypothyroidism due to increased thyroid activity to maximize iodine uptake and recycling 1
- This deficiency increases the risk of developing autonomous thyroid nodules that become unresponsive to TSH control 1
- Iodine deficiency remains prevalent in 75% of people with goiter who live in less developed countries 2
Nutritional Deficiencies Beyond Iodine
- Iron deficiency impairs thyroid metabolism and contributes to goiter development 1
- Selenium deficiency affects thyroid function as deiodination of T4 to T3 depends on Type 1 5'-deiodinase, a selenoenzyme 1
Demographic Risk Factors
- Female sex is a significant risk factor, with colloid goiter being more common in women, particularly in their fifth and sixth decades 1
- Advancing age increases goiter incidence, with typical development occurring over many years 1
Pathophysiological Mechanism
TSH-Mediated Colloid Accumulation
- Contrary to older beliefs, colloid goiters can form under continuous TSH stimulation without a previous hyperplastic phase 3
- Thyroglobulin reaccumulation occurs despite continuous heavy TSH stimulation if there is concomitant organification of at least some iodine 3
- Endocytosis gradually becomes refractory to continuous TSH stimulation when minimal iodine is available for organic binding 3
Important caveat: The traditional view that colloid accumulation and intense TSH stimulation are mutually exclusive has been revised—primarily colloid-rich goiters may form in the presence of continuously elevated TSH levels 3
Management Approach
Initial Assessment
- TSH is the appropriate first test for all patients with goitre 4
- If TSH is low, a radionuclide scan is helpful 4
- Thyroid ultrasound should be performed in all patients with goitre as it has become an extension of physical examination 4
Treatment Options Based on Etiology
- Iodine supplementation for iodine-deficient goiters 4
- Observation for asymptomatic cases 4
- Thyroxine suppression in selected cases 4
- Surgery for compressive symptoms (cough, dysphagia) or when malignancy cannot be excluded 4
Critical pitfall: In iodine-sufficient areas, goiters may be associated with autoimmune thyroiditis, hypothyroidism, hyperthyroidism, and thyroid carcinoma—these require different management strategies than simple iodine deficiency 2