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Thickness changes in cell membranes, usually encountered in phase transition of lipid bilayers, maybe initiated by conformational changes of some domains forming membrane receptors responding as a secondmessenger to external ligands. Unfortunately, thinning may indicate the possibility of fracture of the membrane,leading to loss of functionality of the cell aggregate. The mentioned response, whose manifestation is cAMP(cycling Adenosine MonophosPhate), may be directly linked to the coupling of conformational and mechanicaleffects, the former arising in some of the domains cited above. Stationarity of a new Helmholtz free energy,accounting for receptor density and conformation field and strain gradients in membrane thinning orthickening, is investigated. It turns out that the density of active receptors is directly related to the conformationfield above and it enters as a source term in the resulting balance equation for the membrane stress. Henceforth,balance laws for the cAMP transporters and for the flux of active receptors, coupled with the former, must besupplied together with a balance between the diffusive powers to yield “sink” due to the outgoing flux providedby the transporters.