MRI is universally used in postoperative care pituitary adenomas, for the diagnosis of residual or recurrent tumors [11, 12]. This retrospective cohort study conducted among 44 patients who underwent TSS due to non-functional pituitary macroadenoma indicated post-operative TSH and prolactin levels are more likely to be associated with some MRI characteristics before surgery namely size and volume of the tumor. Moreover, size and volume of tumor in MRI images before trans sphenoidal surgery (TSS) showed an adverse association with the percentage of normal residual of pituitary gland. In the conducted study by Di Maio et al. in 2012, NRPG was identified in 79% of the patients on preoperative MRI . Our research showed that NRPG was diagnosed in 21.4% of the patients on postoperative MRI, and there was a strong significant relationship between the size and volume of the tumor before surgery and NRPG. MRI with or without administration of gadolinium contrast agent also allows accurate assessment of the position and function of the tumor before and after surgery [12, 13]. But gadolinium uptake significantly improves diagnosis of the pituitary gland, especially in severe deformity cases of the pituitary gland. Improved diagnosis of the pituitary gland, after gadolinium uptake is due to the rapid and pronounced contrast of the pituitary gland, which is more than the adenoma .
In the study performed by Nomikos et al. in 2004, 721 patients with non-functional macroadenoma pituitary surgery were evaluated. 24.4% of patients had hypothyroidism after surgery, the prevalence of which was lower than our study (61.9%). Also in the Nomikos study, 1 year after surgery, preoperative prolactin levels were slightly increased in 25.3% (only 5 patients); increasing preoperative and postoperative prolactin was observed in 45% and 27.5% of patients in the present study, respectively; that was more that Nomikos study .
In 2015, Lee et al. conducted a study on 45 patients undergoing sphenoid surgery. In this study, hypogonadism was defined as total serum testosterone level < 4.2 ng/ml. Tumor volume was calculated based on MRI images before and after surgery. Examination of the MRI results showed that the need for long-term postoperative testosterone replacement was significantly associated with a larger volume of preoperative tumor and preoperative testosterone levels. Preoperative tumor volume and testosterone levels affect postoperative hypogonadism. By measuring tumor volume and testosterone levels, surgeons will be able to predict postoperative hypogonadism and the need for long-term hormone replacement .
In 2021, Ono et al. examined the clinical features and surgical outcomes of 79 patients with dysfunctional pituitary adenoma. Reduction of growth hormone levels was observed in 37.7% of patients. In our study, also a deficiency of postoperative IGF-1 was observed in 12% of patients, which indicated a lower prevalence of this disorder in the present study. Ono et al. also showed that, hypogonadism after surgery was developed in 19% of patients, but in our study, the prevalence of hypogonadism was 54.8% postoperatively, which was higher than the Ono et al. results. A deficiency of TSH was observed in 6.3% of patients in the Ono et al. results, deficiency of TSH was 61.9% in patients studied in our research, and this matter indicates the higher prevalence of this disorder in our study with compared with Ono et al.  results.
In other hand, one of the most common symptoms of dysfunctional pituitary macroadenomas is hypogonadism, which may require long-term hormone replacement. In addition, reducing the pressure on the normal pituitary gland may lead to postoperative recovery of the pituitary gland [15, 17].
The rate and type of changes in hormone’s level after surgery can be different because pituitary function and preservation of normal pituitary tissue after surgery depends on several factors such as tumor characteristic, the amount of pressure caused by the tumor on normal pituitary tissue, the type of surgery selected (for example, in patients undergoing cranial surgery, the incidence of this deterioration is significantly higher) and the age of patients [7, 13, 18, 19].
For example in study performed by Jahangiri et al. in 2016, patients with preoperative endocrine deficits (n = 153, 50%) were significantly older (mean age 60) and had larger adenomas. Postoperative endocrine deficits occurred in 42 (13.7%) patients (Thyroid axis 3%, cortisol axis 6%, and GH/IGF-1 axis 4%). In our study, decreased cortisol was observed in 32.3% and 48.8% of patients before and after surgery, respectively and a deficiency of postoperative IGF-1 was observed in 12% of patients. In similar to Jahangiri et al.  results, deficits were occurred in hormones production. Disorders of cortisol levels can also vary before and after pituitary surgery. For example, in patients who have had low blood pressure during anesthesia, or who have been taking medications such as phenytoin, ketoconazole, corticosteroid, and narcotics, the disorder is more pronounced [21, 22].
Guinto-Nishimura et al. in 2020 performed preoperative MRI in patients with non-functional pituitary macroadenoma to determine tumor severity alone and in association with the right cerebellar peduncle in 26 patients. Tumor consistency was assessed as soft in 20 (76.92%) patients. In the present study, 93% of the tumors had a soft consistency, which was higher than the Guinto-Nishimura study. Guinto-Nishimura et al. also showed that preoperative tumor volume was 28.7 ± 26.3 cm3 and the rate of tumor resection was not significantly associated with tumor consistency .
Onofrj et al. in 2018 reported that the mean preoperative tumor volume was 24.66 cm3. A progressive tumor volume decrease was noted during follow-up, and symptoms improved in 78% of patients. They conducted the duration of symptoms prior of surgery is a more important factor than tumor resection volume alone when considering the long-term outcome of symptoms. In our study preoperative mean tumor volume was 6845.5 mm3 and a significant relationship was observed between preoperative tumor volume and postoperative production of prolactin hormone .
Juthani et al. in 2020 performed a study on the 212 patients with pituitary MRI before and after surgery. 62% of patients underwent resection of the tumor based on postoperative MRI findings and comparison with preoperative resection, and as a result, the remnants of the tumor had to be removed. Tumor resection due to postoperative MRI results was significantly associated with increased survival and pituitary function as well as hormone therapy. These results suggest that using preoperative MRI is a safe method leading to the increase in the resection rate of pituitary adenomas. Especially when MRI is combined with endoscopy, it provides the ability to adapt to the removal of tumors while optimizing pituitary function, resulting in a high rate of recovery of secretory hormone .
In the results of the present study, normal tissue was not observed in 21.4% of MRI cases after surgery. MRI with or without administration of gadolinium contrast agent also allows accurate assessment of the position of the tumor before surgery and staging of pituitary tumors [13, 23]. Manifestations of normal pituitary gland tissue on MRI images include the size and shape of the gland reflecting pituitary function, which depends on the patient's position, the intensity of the adenohypophysis and neurohypophysis signals .
Given the prevalence of pituitary adenomas and especially their non-functional types, often diagnosed at higher stages, pre- and post- operative MRI scan can be used to choose the right treatment approach before.