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In the present study we aimed to investigate plasma levels of CGRP during headache induced by the NO donor glyceryl trinitrate ( GTN ) in 16 patients with chronic tension - type headache and 16 healthy controls .
 Disease: headache; Chemical: NO; Chemical: glyceryl trinitrate; Chemical: GTN; Disease: tension - type headache
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Disease: headache; Chemical: NO; Chemical: glyceryl trinitrate; Chemical: GTN; Disease: tension - type headache