Aldosterone Resistance in Preterm Infants
Condition: Newborn
MeSH terms: Premature Birth
Study type: Observational

Summary: 
      In the neonatal period, the human kidney is characterized by a functional immaturity
      responsible for an impaired ability to regulate water and sodium homeostasis, which is
      exacerbated by prematurity. This altered sodium handling could be related to a partial renal
      aldosterone resistance. Renal sodium reabsorption and potassium excretion are mainly
      controlled by aldosterone, after binding to the mineralocorticoid receptor (MR). The
      investigators have analyzed MR expression throughout human and mouse renal development, and
      the investigators found a weak MR expression at birth. The investigators have conducted a
      pilot study in full-term newborns, which confirmed a partial neonatal aldosterone resistance.
      This study also highlighted that urinary aldosterone is the best index to accurately assess
      aldosterone sensitivity at birth.
    

Detailed description: 
      Principal objective:

      To assess aldosterone resistance at birth by a non invasive measurement of urinary
      aldosterone, in order to evaluate its intensity as a function of gestational age.
      Determination of normal values of urinary aldosterone concentration in each group.

      Secondary objectives:

      Comparison of plasma and urinary electrolytes concentrations with hormonal measurements and
      clinical parameters. Evolution of these biological parameters throughout the first year of
      life, depending on gestational age at birth.

      Methodology : multicentric study, open study Two hundred-forty newborns will be included in
      order to constitute 4 groups of 60 children, classified according to their gestational age: <
      28 GW, 28 - < 33 GW, 33- < 37 GW, > 37 GW.

      Inclusion criteria: every newborn will be included, after written parental consent was
      obtained.

      Study :

      Urinary samples will be collected onto a gauze compress, during the first 24 hours of life,
      at day three, and at 1, 3, 6 and 12 months. A blood sample will be obtained from systematic
      umbilical cord blood collection at birth and during the Guthrie test at day three.
      Aldosterone and renin concentrations will be measured in BICETRE Hospital laboratory. Plasma
      and urinary electrolyte concentrations will be measured in the Biochemistry department. DNA
      samples will also be gathered from umbilical cord blood for future genetic investigations
      (functional polymorphisms of the MR gene).

      Perspectives This study will permit to assess the intensity of aldosterone resistance in
      full-term and preterm newborns, by a non invasive method. It should bring new insights into
      the mechanisms of hormonal regulation of sodium balance in preterm newborns and during the
      first year of life. Urinary aldosterone assessments may open new perspectives for therapeutic
      management of water and sodium waste in premature infants.
    

Observational model: Case-Only
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Every newborn without congenital malformation will be included, after written parental
        consent was obtained
      
Biospecimen description: 
      -  Urinary samples will be collected onto a gauze compress, during the first 24 hours of
           life, at day three, and at 1, 3, 6 and 12 months.

        -  A blood sample will be obtained from systematic umbilical cord blood collection at birth
           and during the Guthrie test at day three
    
Keywords: Non Invasive measurement; Preterm infants; Aldosterone resistance