Protein metabolism in Turner syndrome and the impact of hormone replacement therapy.
BACKGROUND
Studies have documented an altered body composition in Turner syndrome (TS). Body fat is increased and muscle mass is decreased. Ovarian failure necessitates substitution with female hormone replacement therapy (HRT), and HRT induces favourable changes in body composition. It is unknown how HRT affects protein metabolism.


OBJECTIVE
To test whether alterations in body composition before and after HRT in TS are a result of altered protein metabolism.


METHODS
We performed a randomized crossover study with active treatment (HRT in TS and oral contraceptives in controls) or no treatment.


METHODS
We studied eight women (age 29.7 +/- 5.6 (mean +/- SD) years) with TS, verified by karyotype, and eight age-matched controls (age 27.3 +/- 4.9 years). All subjects underwent a 3-h study in the postabsorptive state. Protein dynamics of the whole body and of the forearm muscles were measured by an amino acid tracer dilution technique using [(15)N]phenylalanine and [(2)H(4)]tyrosine. Substrate metabolism was examined by indirect calorimetry.


RESULTS
Energy expenditure was comparable among TS and controls, and did not change during active treatment. Whole-body phenylalanine and tyrosine fluxes were similar in the untreated situations, and did not change during active treatment. Amino acid degradation and protein synthesis were similar in all situations. Muscle protein breakdown was similar among groups, and was not affected by treatment. Muscle protein synthesis rate and forearm blood flow did not differ among groups or due to treatment.


CONCLUSIONS
Protein metabolism in TS is comparable to controls, and is not affected by HRT.
Gravholt
Claus Højbjerg
CH
Medical Department M (Endocrinology and Diabetes) and Medical Research Laboratories, Aarhus Sygehus NBG, Aarhus University Hospital, Aarhus C, Denmark. ch.gravholt@dadlnet.dk
Riis
Anne Lene
AL
Møller
Niels
N
Christiansen
Jens Sandahl
JS
D000328:Adult; D001823:Body Composition; D002153:Calorimetry, Indirect / Q000379:methods; D018592:Cross-Over Studies; D003903:Deuterium; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D004967:Estrogens / Q000627:therapeutic use*; D005260:Female; D020249:Hormone Replacement Therapy / Q000379:methods*; D006801:Humans; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism*; D009587:Nitrogen Isotopes; D010649:Phenylalanine / Q000493:pharmacokinetics; D011374:Progesterone / Q000627:therapeutic use*; D011506:Proteins / Q000378:metabolism*; D014424:Turner Syndrome / Q000188:drug therapy* / Q000378:metabolism*; D014443:Tyrosine / Q000493:pharmacokinetics; D055815:Young Adult
D004967:Estrogens; D009587:Nitrogen Isotopes; D011506:Proteins; D014443:Tyrosine; D010649:Phenylalanine; D011374:Progesterone; D003903:Deuterium