Adrenal and thyroid axis function in preterm ventilated baboons

Area of Science:

• Endocrinology
• Neonatal Physiology
• Comparative Medicine

Background:

• Cortisol and thyroid hormones are vital for fetal development and neonatal adaptation.
• Preterm birth often leads to abnormal hormone levels and responses.
• Understanding hormonal responses in preterm neonates is crucial for clinical management.

Purpose of the Study:

• To assess the hypothalamic-pituitary-adrenal (HPA) and thyroid axes' response to stimulation in preterm baboons.
• To evaluate hormonal responses independent of uncontrolled antenatal events.
• To investigate the impact of antenatal betamethasone and postnatal thyroxine (T4) treatment.

Main Methods:

• Preterm baboons delivered at 125 days gestation underwent ACTH, CRH, and TRH stimulation tests.
• Animals received surfactant treatment and ventilation for up to 14 days.
• Hormonal responses (cortisol, T4) were measured following various stimulation protocols.

Main Results:

• Baseline cortisol levels were elevated, indicating stress, by day 5.
• Consistent cortisol increase occurred only after 11 days in response to high-dose CRH or ACTH.
• Postnatal T4 treatment suppressed cortisol responses and lowered baseline T4 levels.

Conclusions:

• The HPA axis is immature in preterm baboons, showing unresponsiveness to standard stimulation until 11 days of age.
• Thyroxine treatment can influence both the HPA axis and thyroid hormone levels in preterm neonates.
• This study provides insights into hormonal development and response in a preterm primate model.