Tri-iodothyronine and thyroxine in human milk

Area of Science:

• Endocrinology
• Human milk analysis
• Neonatal nutrition

Background:

• Thyroid hormones are vital for infant development.
• Human milk is a primary source of nutrition for infants.
• Understanding thyroid hormone content in milk is important for infant health.

Purpose of the Study:

• To quantify tri-iodothyronine (T3) and thyroxine (T4) concentrations in human milk.
• To evaluate analytical methods for accurate hormone measurement in milk.
• To assess variations in T3 levels between colostrum and mature milk.

Main Methods:

• Radioimmunoassay (RIA) was used for hormone quantification.
• T3 analysis was performed on both unextracted and extracted milk samples.
• Ethanol extracts of defatted milk provided reliable T3 measurements.

Main Results:

• Tri-iodothyronine (T3) was detected in human milk samples.
• Mean T3 levels in colostrum were 0.80 nmol/l (early) and 0.93 nmol/l (hind milk).
• Mean T3 in mature milk was 1.19 nmol/l; thyroxine (T4) was not detected (limit 3 nmol/l).

Conclusions:

• Human milk contains measurable levels of T3, with higher concentrations in mature milk compared to colostrum.
• Accurate T3 quantification in milk necessitates extraction to avoid analytical artifacts.
• Thyroxine (T4) is undetectable in human milk using standard RIA methods, suggesting limited contribution from milk.