A retrospective study was carried out on 79 patients with a history of mold exposure, fatigue, and chronic rhinosinusitis (CRS) to determine whether there is a causal relationship between fungal exposure and chronic sinusitis, fatigue, and anterior hypopituitarism, especially growth hormone deficiency (GHD). Of the patients, 94% had a history of CRS, endoscopically and/or computed tomography (CT) confirmed; 100% had chronic fatigue and 100% had either significant history of indoor mold exposure and/or positive mold plate testing as measured by settle plates, with an average colony count of 21 (0-4 normal). A total of 62 had positive mold plate testing and 17 had positive history of mold exposure. Of 75, 73 (97.3%) had positive serum immunoglobulin G (IgG)-specific antibodies to fungal antigens. Out of 8, 7 were positive for urinary trichothecenes. Resting levels of insulin-like growth factor 1 (IGF-1) averaged 123 ng/mL (range 43-285, normal 88-249 ng/mL). Despite normal resting levels of IGF-1, significant deficiency of serum human growth hormone (GH) was confirmed by insulin tolerance test (ITT) in 40 of 50 tested. In all, 51% (40/79) were GH deficient. Primary or secondary hypothyroidism in T3 and/or T4 was seen in 81% (64/79) patients; 75% (59/79) had adrenocorticotrophic hormone (ACTH) deficiency. Fungal exposure endocrinopathy likely represents the major cause of GHD, affecting approximately 4.8 million people compared to approximately known 60,000 cases from all other causes. A literature review indicates a possible mechanism of GHD in fungal exposure is that the fungal glucan receptors in the lenticulostellate cells of the anterior pituitary bind to fungal cells wall glucans and activate the innate immune system, which activates macrophages that destroy the fungus and lenticulostellate tissue. Treatment of patients included normal saline nasal irrigations, antifungal and antibiotic nasal sprays, appropriate use of oral antibiotics and antifungals, facial steamer with CitriDrops. Thymate and/or Intramax vitamin supplements, hormone replacement, and reduction of indoor mold levels. Resolution of rhinosinusitis was seen in 93% (41 of 45) of the patients who achieved a mold count by settling plates of 0-4 colonies. Thirty patients were unable to lower their mold counts below four colonies and had various degrees of mucosal disease and fatigue remaining. Fatigue was improved in all 37 patients who received GH and cortisol and/or thyroid hormone, which were deficient. Fatigue was partially relieved in 7 of the 37 who did not achieve mold counts of fewer than four colonies.