P-piller kan hindre muskelvekst

Denne studien så også på proteinsyntesen i muskler, og etter en enkelt treningsøkt med beinspark (leg extension) så man lavere muskelvekst hos de som tok p-piller, men det var ingen forskjell på proteinnedbrytning. P-piller med høyere doser av østrogen hemmer de androgene hormonene androstenedion og testosteron så det er sannsynligvis både direkte og indirekte årsaker til at dette skjer. Progesteron ser ut til å ha en såkalt Bell-kurve effekt, lave doser hemmer muskelvekst, moderate doser kan faktisk stimulere muskelvest, mens veldig høye doser kan hemme muskelvekst igjen.

Ut fra de doseringer jeg har sett kan det virke som Yasminelle (20mcg ethinyløstradiol) og Yasmin (30mcg ethinyløstradiol) er de beste preparatene for å redusere den hemmende effekten på proteinsyntese. Virkestoffet drospirenon som brukes i disse preparatene er en såkalt analog til spironolacton, som hemmer aldosteron og dermed har enn diuretisk (vanndrivende) effekt.

J Med Sci Sports. 2009 Oct 22.

Effect of administration of oral contraceptives on the synthesis and breakdown of myofibrillar proteins in young women.

Hansen M, Langberg H, Holm L, Miller BF, Petersen SG, Doessing S, Skovgaard D, Trappe T, Kjaer M.

Institute of Sports Medicine, Bispebjerg Hospital, Copenhagen, Denmark.

Oral contraceptive (OC) treatment has an inhibiting effect on protein synthesis in tendon and muscle connective tissue. We aimed to investigate whether OC influence myofibrillar protein turnover in young women. OC-users (24+/-2 years; Lindynette((R))n=7, Cilest((R))n=4) and non-OC-users (controls, 24+/-4 years n=12) performed one-legged kicking exercise. The next day, the myofibrillar protein fractional synthesis rate (FSR) was measured using stable isotopic tracers ((13)C-proline) while the subjects were fed standardized nutrient drinks. Simultaneously, a marker for myofibrillar protein breakdown, 3-methyl-histidine (3-MH), was measured in the interstitial fluid of the vastus lateralis. Measurements were performed in both legs. In general, myofibrillar protein FSR was lower in OC-users (two-way analysis of variance, P<0.05), although the difference seemed to depend on the OC type. Interstitial 3-MH in the skeletal muscle was not different between groups and did not vary by OC type. Exercise did not change myofibrillar protein FSR or 3-MH concentrations. Serum androstenedione and bioavailability of testosterone were lower in OC-users. In conclusion, the results indicate that the use of OC has an inhibiting effect on myofibrillar protein synthesis and the magnitude of the effect may depend on the type of OC. In contrast, there was no effect of OC on myofibrillar protein breakdown in the fed state.