Endocrine Abstracts

Background: Several studies have documented an altered body composition in Turner syndrome (TS), a model of premature ovarian failure. Body fat is increased and muscle mass is decreased. The ovarian failure necessitates substitution with female hormone replacement therapy (HRT) for a number of years, and HRT induces favourable changes in body composition with a decrease in body fat and an increase in fat free mass. It is unknown how HRT affects protein metabolism.

Aim: To study protein metabolism in TS in detail, and evaluate the distinct impact of HRT action.

Design: Randomized crossover study with active treatment (HRT in TS and P-pill in controls) or no treatment for 2 month each.

Material: We studied women with Turner syndrome (n=8, age 29.7±5.6 (mean±S.D.) years), verified by karyotype, and age-matched controls (n=8, age 27.3±4.9 years).

Methods: All subjects underwent a 3-h study in the postabsorptive state. After regional catheterization, protein dynamics of the whole body and of the forearm muscles were measured by amino acid tracer dilution technique using [¹⁵N]phenylalanine and [²H₄]tyrosine. Substrate metabolism was examined by indirect calorimetry.

Results: Estradiol increased and FSH decreased during active treatment in TS. 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 (TS vs C: 4.0±0.9 vs 4.8±0.8 μmol*kg⁻¹*h⁻¹, P=0.1) and protein synthesis (36.8±5.2 vs 35.2±3.0 μmol*kg⁻¹*h⁻¹, P=0.5) was similar in the untreated situations and did not change during treatment. 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 a short course of HRT.