Which human body hormonal systems exhibit 24 hour diurnal cyclical activity?
The real answer is probably more than you want, but its easy to do better than the list above.  

I took a look through GEO for human circadian expression data and surprisingly I only found 2.

Looking at GSE2703 - the rhesus circadian expression experiment, they have shown 355 genes that are rhythmically expressed.  This is not a great experiment because they only looked over a single 24 hour period.  Its only the adrenal gland.  Nonetheless they found 355 genes which seemed to be circadian.  the table is supplemental data to the article,  listed below. 

I see a fibroblast growth factor receptor, some hydrocarbon nuclear receptor components, sterol regulatory factors, bone morphogenic protein 2, glutamate receptor, thrombonspondin receptor, ryanodine receptor 3 (what is that?) , lysophosphatidic acid G-protein-coupled receptor 2, purinergic receptor P2Y, G-protein coupled.  You might find more if you know what you are looking for. 

The other circadian study was on human muscle, which will no doubt give different answers.  I imagine circadian behavior is highly tissue dependent. 

Reference: Lemos DR, Downs JL, Urbanski HF. Twenty-four-hour rhythmic gene expression in the rhesus macaque adrenal gland. Mol Endocrinol 2006 May;20(5):1164-76