Are desires influenced by beliefs? I refer it especially to what men and women look for in the partner. Of course, this is a generalized speech. 

There is a correlation between the model of beauty proposed to men and what men sees as beauty. And, as well, there seems to be a strong correlation between what women search and what soap opera propose as the winning model.

Which is the cause and which is the consequence? Mass media propose what people already desire? Does this affect people desire? Can it be considered a loop?

I think the question can be answered by comparing different stile of life across countries and centuries. For example the desire of being slim (see the growth of speaking about liposuction) has increased when the idea of beauty has become a synonim of being very slim.

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Is there any element to hypothesize that a person's desire is bound to his internal dialogue? To his fears? To his beliefs? To what he perceive as needs?
This is a very big and broad question in terms of the fundamentals that underpin it, which are basically nature vs nurture based. There are some desires we have that are innate and core to our being, and then there are desires that are learned. The interaction between them is very complex, but you can give some obvious examples of how both are important. On all of these, there's heaps of research, but any research is complicated because the interaction between nurture and nature is so complicated.

The human being can rewire almost any impulse. This is what is so special about the human being, and which is why cultures vary so hugely. 

An obvious example is a young girl lead to believe to be too fat, proven to be thanks to a broken capacity of seeing themselves properly, and this cancelling out her innate motive to eat. However, if you want to look at the mechanics of how that works, you'll see a hugely complex interaction of genetic, biological, and environmental factors at play, as this wiki section shows very clearly: http://en.wikipedia.org/wiki/Anorexia_nervosa#Causes 

To continue towards your actual question, if you take that mechanism to mass media, you have to look at the motivations of the whole industry. It is in the mass media's interest to provide you with new reasons to consume them. A human being has natural impulses to be stimulated as well as comforted, so it will be attracted to everything that does either or both. And then there are companies that make things for consumption that have long ago discovered that mass media are an efficient way to help make you want to consume their product. 

In the whole sea-change of evolution and invention, things are always changing enough for people to look for new (or new-looking) solutions to (new or old) problems or the satiation of an innate desire (eating fat or sugar, finding a mate, standing out or blending in socially, etc.). The power of mass media and marketing comes from bridging the distance between what they are ready to offer that is different enough from what's already out there and the desire you want to satiate. 

So yes, the loop / spiral is very likely the best way to describe the interaction. And it can lead to some pretty excessive and problematic behavior with all three parties involved.