Thyroid function in a cassava-eating population affected by epidemic spastic paraparesis

Area of Science:

• Endocrinology
• Nutritional Science
• Toxicology

Background:

• A rural population in Mozambique experienced an epidemic of spastic paraparesis linked to dietary cyanide from cassava.
• High levels of serum and urinary thiocyanate were observed, confirming significant cyanide exposure.

Purpose of the Study:

• To investigate thyroid function in a population with heavy cyanide exposure.
• To determine the impact of adequate iodine intake on thyroid adaptation to thiocyanate.

Main Methods:

• Assessed thyroid hormone levels (FT4I, FT3I, TSH) and urinary iodine excretion in a sampled population.
• Conducted a follow-up study on school children to confirm findings on thiocyanate exposure and iodine intake.
• Monitored for the presence of goitre.

Main Results:

• Serum and urinary thiocyanate levels were very high, indicating substantial cyanide exposure.
• Urinary iodine excretion was normal, suggesting adequate iodine intake.
• Serum FT4I levels were slightly decreased, while FT3I, T3/T4 ratio, and TSH were slightly elevated, indicating adaptation rather than overt hypothyroidism.
• No endemic goitre was observed in the school children.

Conclusions:

• Adequate iodine supply enables the thyroid gland to adapt to high thiocyanate body burden.
• Overt hypothyroidism and goitre can be prevented even with heavy cyanide exposure if iodine intake is sufficient.