Related Experiment Videos
Impaired urinary cortisol excretion and early cardiopulmonary dysfunction in immature baboons
BradleyA Yoder1, Helen Martin, Donald C McCurnin
1Department of Pathology, University of Texas Health Science Center, San Antonio, TX 78284, USA. yoder@pathology.uthscsa.edu
Insights
Immature baboons with low urinary cortisol excretion rates (UCER) showed poor cardiovascular function. Early hydrocortisone treatment improved their condition, suggesting this model for preterm infants with adrenal insufficiency.
Area of Science:
- Neonatal Physiology
- Endocrinology
- Cardiovascular Research
Background:
- Early adrenal insufficiency in premature infants is linked to cardiopulmonary dysfunction.
- Standard cortisol and ACTH tests may not fully capture developing adrenal function or identify at-risk infants.
- The ontogeny of postnatal cortisol secretion requires further investigation in immature models.
Purpose of the Study:
- To determine the postnatal urinary cortisol excretion rate (UCER) from birth to 14 days in immature baboons.
- To evaluate the relationship between UCER and cardiac performance in these animals.
- To assess the utility of immature baboons as a model for human preterm infants.
Main Methods:
- Assessed 6-hour blocked urinary cortisol excretion rate (UCER) in 21 premature baboons (125-day gestation).
- Measured urinary cortisol via radioimmunoassay (RIA) and performed serial echocardiograms.
- Administered hydrocortisone to a subgroup for refractory hypotension and compared outcomes.
Main Results:
- UCER significantly increased from 0-6 hours to 66-72 hours in non-treated baboons.
- Infants requiring cortisol treatment exhibited reduced UCER between birth and 24 hours.
- Cortisol-treated infants showed impaired cardiac function, lower blood pressure, and metabolic acidosis.
Conclusions:
- Adrenal cortisol secretion matures significantly within the first 72 hours of life in immature baboons.
- Delayed UCER increase correlates with poor cardiovascular function, responsive to hydrocortisone.
- The immature baboon serves as a relevant model for studying postnatal adrenal hypofunction in preterm humans.
Abstract:
Early adrenal insufficiency is associated with cardiopulmonary dysfunction in immature infants. Isolated cortisol levels and ACTH stimulation testing may not adequately show ontogeny of postnatal cortisol secretion nor identify at risk infants. Our objectives were 1) to determine postnatal urinary cortisol excretion rate (UCER) from birth to 14 d in immature baboons and 2) to evaluate the relation between UCER and cardiac performance. UCER was assessed via 6-h blocked urine collections from birth to 336 h of age in twenty-one 125-d gestation (term = 185 d) baboons. Urinary cortisol was measured by RIA. Cardiopulmonary parameters were averaged over the same time periods as urine collection. Serial two-dimensional echocardiograms were performed. After 24-h age, a subgroup (n = 8) received up to four doses (0.5-1.0 mg/kg each) of hydrocortisone for refractory hypotension. UCER significantly increased from 0 to 6 h through 66 to 72 h age for non-cortisol-treated infants. Significantly reduced UCER patterns between birth and 24 h were found for animals subsequently requiring cortisol treatment. Cortisol-treated infants had lower mean blood pressure, worse metabolic acidosis, increased fluid needs, and impaired left ventricular function between 12 and 48 h of age. No group differences were found in gas exchange or ventilator support. We conclude that adrenal cortisol secretion significantly improves over the initial 72 h of life in the 125-d immature baboon. Failure to increase UCER after 12-24 h of life correlated with poor cardiovascular function that improved with hydrocortisone therapy. Adrenal hypofunction in the immature baboon is similar to the very preterm human and could serve as a model for future postnatal investigations.