Some people, managed for years for IBS, may have non-celiac gluten sensitivity (NCGS).  Gastrointestinal symptoms of IBS are clinically indistinguishable from those of NCGS, but the presence of any of the following non-intestinal manifestations suggest a possible NCGS: headache or migraine , "foggy mind", chronic fatigue ,  fibromyalgia ,    joint and muscle pain,    leg or arm numbness ,    tingling of the extremities,   dermatitis ( eczema or skin rash ),   atopic disorders ,  allergy to one or more inhalants, foods or metals   (such as mites , graminaceae , parietaria , cat or dog hair, shellfish , or nickel  ), depression ,    anxiety ,  anemia ,   iron-deficiency anemia , folate deficiency , asthma , rhinitis , eating disorders ,  neuropsychiatric disorders (such as schizophrenia ,   autism ,    peripheral neuropathy ,   ataxia ,  attention deficit hyperactivity disorder  ) or autoimmune diseases .  An improvement with a gluten-free diet of immune-mediated symptoms, including autoimmune diseases, once having reasonably ruled out coeliac disease and wheat allergy , is another way to realize a differential diagnosis. 
It should be noted that in theory if one was to consistently suppress your natural estrogen levels for a long period of time, this would negatively impact your health, including your cholesterol. Due to the ability of Letrozole- to inhibit estrogen so much, this should definitely be a concern to most users. However the research that has focused on the relationship between use of letrozole and cholesterol levels is rather inconsistent in it's findings. Many studies have concluded that the compound is detrimental to both a user's HDL and LDL cholesterol levels, while other research has found no link. Obviously individuals are best served to monitor their cholesterol while using any compound via blood tests however barring that, letrozole should simply not be run for extended periods of time if at all possible. Doing so could cause serious medical complications.
Along with the issues related to blood lipids is the fact that many users complain that their libido is dramatically reduced when using the compound. This is related to the fact that estrogen is partly responsible for the regulation of an individual's sex drive. Since Letrozole- is so potent it can often drive estrogen levels too low and this inhibits a user's libido. To avoid this users can lower dosages, but some anecdotally report that even extremely low doses of the drug can cause problems. If this is the case a less potent compound such as exemestane or anastrozole may be a more appropriate option.