98694
Initially , it was believed that growth hormone actually prolonged lifespan due to a 1990 study that indicated that injection of growth hormone to men over 60 years of age appeared to reverse various biomarkers implicated in aging , such as decreased muscle mass , bone density , skin thickness , and increased adipose tissue .
 decreased muscle mass
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 decreased muscle mass