When you are an endocrinologist you know that hormones are released into the circulation in pulses and that melatonin is only produced in the dark, that glucocortoids concentrations in the blood are high during the night and low during the day, that many hormones have their rhythm. Every hormone has its time, as the prophet sayed.

However, what has not been known until now is that to the same extend more than 40 % of all genes are expressed in a circadian (day long) rhythm.  Zhang and colleagues measured in the mouse ( and the might be the only shortcoming of the study ) the gene expression with arrays to determine many gene simultaneously in every hour of the day and night. They found 43 % of all genes expressed in a circadian rhythm. They also determined noncoding RNAs  and found 1000 of them cycling.

There are consequences for medicine and therapy: The targets of the top most drugs are expressed all in (specific) rhythms: When a drug like aspirin for example is taken at the wrong time, it would be gone before the target is fully expressed. The scale of this problem seems tremendous. Any pharmaceutical company has to do its home work again. But on the other hand, therapy might become more reliable which would be a large improvement.

The circadian rhythm in the 12 organs analysed are quite different. It might take some time to get used to the thinking that genes in question are not stable during the day but change the level of expression. It will be interesting to follow the aftermath of that paper. The paper is open access and therefore free to everybody.

A must.