Relationships between birthweight and plasma thyroxine, triiodothyronine and iodide concentration in lambs

Area of Science:

• Animal Science
• Endocrinology
• Neonatal Physiology

Background:

• Thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are critical for mammalian development.
• Postnatal adaptation involves significant physiological changes, including endocrine regulation.
• Gestational age at birth can influence neonatal outcomes and endocrine status.

Purpose of the Study:

• To investigate the relationship between birth weight and plasma thyroid hormone concentrations in crossbred lambs.
• To examine the impact of gestational age on early postnatal thyroid hormone levels.
• To assess the influence of maternal milk intake on plasma iodide concentrations.

Main Methods:

• Blood samples were collected from crossbred lambs at different time points post-birth.
• Plasma concentrations of thyroxine (T4), triiodothyronine (T3), and iodide were measured.
• Lambs were categorized based on gestational age at spontaneous birth (days 143, 145, 147).

Main Results:

• Plasma T4 and T3 concentrations were similar across lambs born on days 143, 145, or 147 of gestation in the immediate hours after birth.
• A positive linear relationship was found between birth weight and plasma T4 or T3 concentrations within 72 hours post-delivery for lambs born on day 145.
• Plasma iodide concentrations peaked within 6 hours post-birth, correlating with iodine absorption from maternal milk.

Conclusions:

• Birth weight is a significant factor influencing thyroid hormone levels in lambs born at specific gestational ages (day 145).
• Early postnatal thyroid hormone status is influenced by both birth weight and potentially gestational maturity.
• Maternal milk is a crucial source of iodine for lambs, impacting early postnatal iodide levels.