Congenital Iodine Deficiency Syndrome (Endemic Cretinism)

Congenital iodine deficiency syndrome (CIDS), historically known as cretinism, is a condition present at birth characterised by impaired physical and mental development due to insufficient thyroid hormone, often stemming from inadequate maternal dietary iodine during pregnancy. This condition falls under the specialty of endocrinology.

Signs and Symptoms

Iodine deficiency often results in the gradual enlargement of the thyroid gland, known as a goitre. Poor growth in length is noticeable from the first year of life, and untreated individuals typically have an adult stature ranging from 100 to 160 cm. Other notable signs include thickened skin, hair loss, an enlarged tongue, and a protruding abdomen. For children, bone maturation and puberty are significantly delayed. In adults, the condition can impede ovulation and lead to infertility.

Mental deterioration is also common. Neurological impairments can range from mild, such as reduced muscle tone and coordination, to severe, where the individual may be nonverbal and reliant on others for basic care. Cognitive impairments can also vary widely, affecting thought processes and reflexes.

Cause

Dietary iodine deficiency is the most common cause of congenital iodine deficiency syndrome globally. Iodine is a very important trace element necessary for the synthesis of thyroid hormones. Its deficiency is the leading preventable cause of neonatal and childhood brain damage worldwide. Although iodine is present in many foods, it is not uniformly available in all soils, particularly in inland, mountainous regions, and areas prone to flooding.

Coastal regions affected by glaciation or heavy rainfall may also have iodine-deficient soils. Populations relying solely on locally sourced food from these areas are at the highest risk of iodine deficiency diseases.

Diagnosis

Differential diagnosis for CIDS includes other causes of dwarfism that may result from malnutrition or various hormonal deficiencies. These include insufficient growth hormone secretion, hypopituitarism, decreased secretion of growth hormone-releasing hormone, deficient growth hormone receptor activity, and downstream causes such as insulin-like growth factor 1 (IGF-1) deficiency.

Prevention

Public health campaigns in numerous countries focus on iodine administration. As of December 2019, mandatory iodine food fortification programmes are in place in 122 countries.

Treatment

In developed countries, congenital iodine deficiency has been nearly eradicated through iodine supplementation of food and newborn screening using blood tests for thyroid function. Treatment involves lifelong administration of thyroxine (T4). For infants, T4 tablets are typically crushed and mixed with breast milk, formula milk, or water.

Formulas containing iron or soya products may necessitate larger doses as they can alter the absorption of thyroid hormone from the gut. Monitoring TSH blood levels every 2–3 weeks during the first months of life ensures affected infants maintain levels at the high end of the normal range.

History

Historically, goitre was a significant marker for iodine deficiency, with treatments dating back to ancient Chinese, Egyptian, and Roman medical texts. The first epidemiological study on CIDS was commissioned by King Carlo Alberto of Sardinia in 1848. Endemic goitre, attributed to dietary monocultures, was prevalent among poorer social classes.

The condition was notably common in southern Europe around the Alps and described by several travellers and physicians in the late 18th and early 19th centuries. The relationship between neurological impairment and hypothyroidism due to iodine deficiency was discovered in the early 20th century, leading to the condition's near elimination in the developed world.

Terminology

The term "cretin" originated from an Occitan and Alpine French expression and was widely used in medical contexts in the 18th and 19th centuries. However, due to its derogatory connotations, modern usage among healthcare professionals has abandoned this term in favour of more appropriate language.

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Self-assessment MCQs (single best answer)

What is the primary cause of congenital iodine deficiency syndrome (CIDS)?

Which organ's enlargement is commonly associated with iodine deficiency?

What is the most common preventable cause of neonatal and childhood brain damage worldwide?

In which areas are populations at the highest risk of iodine deficiency diseases?

What is the differential diagnosis for CIDS most likely to include?

How has congenital iodine deficiency been nearly eradicated in developed countries?

What is the typical treatment for infants diagnosed with CIDS?

Which of the following foods might require larger doses of T4 due to altered absorption of thyroid hormone?

When was the first epidemiological study on CIDS commissioned?

Why has the term "cretin" fallen out of favour in modern medical contexts?