Based on the available information, there is no direct evidence that Lipitor usage affects gym endurance. Lipitor, also known as atorvastatin, is a medication used to treat high cholesterol levels [1]. Its primary function is to lower the levels of low-density lipoprotein (LDL), or "bad" cholesterol, and triglycerides in the blood, thereby reducing the risk of heart disease and stroke [1].

A study published in the Journal of the American College of Cardiology found that statin therapy, which includes Lipitor, did not negatively impact physical performance in healthy individuals [2]. However, it should be noted that this study focused on healthy individuals and not those with pre-existing medical conditions.

Another study published in the Journal of Clinical Lipidology found that statin therapy did not affect muscle strength or physical performance in elderly adults [3]. While this study did not specifically investigate gym endurance, it does suggest that Lipitor usage does not have a significant negative impact on physical performance.

In conclusion, based on the available information, there is no evidence to suggest that Lipitor usage directly affects gym endurance. However, individual experiences may vary, and it is always recommended to consult with a healthcare provider regarding any concerns about medication usage and exercise.

Sources:
[1] <https://www.drugpatentwatch.com/p/tradename/LIPITOR>
[2] <https://pubmed.ncbi.nlm.nih.gov/28807461/>
[3] <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4679305/>