While non-secreting, noninvasive pituitary microadenomas are generally considered to be literally as well as clinically benign, there are to date scant studies of low quality to support this assertion.It has been recommended in the current Clinical Practice Guidelines (2011)  by the Endocrine Society - a professional, international medical organization in the field of endocrinology and metabolism – that all patients with pituitary incidentalomas undergo a complete medical history and physical examination, laboratory evaluations to screen for hormone hypersecretion and for hypopituitarism. If the lesion is in close proximity to the optic nerves or optic chiasm, a visual field examination should be performed. For those with incidentalomas which do not require surgical removal, follow up clinical assessments and  neuroimaging should be performed as well follow-up visual field examinations for incidentalomas that abut or compress the optic nerve and chiasm and follow-up endocrine testing for macroincidentalomas. Ectopic pituitary adenoma
An ectopic (occurring in an abnormal place) pituitary adenoma is a rare type of tumor which occurs outside of the sella turcica, most often in the sphenoid sinus, suprasellar region, nasopharynx and the cavernous sinuses. Metastases to the pituitary gland
Carcinomas that metastasize into the pituitary gland are uncommon and typically seen in the elderly, with lung and breast cancers being the most prevalent, In breast cancer patients, metastases to the pituitary gland occur in approximately 6-8% of cases.Symptomatic pituitary metastases account for only 7% of reported cases. In those who are symptomatic Diabetes insipidus often occurs with rates approximately 29–71%.
And that if this were the case, then the mechanism remains unclear.Administration of nitrous oxide anesthesia can precipitate subacute combined degeneration in people with subclinical vitamin B12 deficiency, while chronic nitrous oxide exposure can cause it even in persons with normal B12 levels. Posterior column dysfunction decreases vibratory sensation and proprioception (joint sense). Lateral corticospinal tract dysfunction produces spasticity and dorsal spinocerebellar tract dysfunction causes ataxia. Cause
In general, the most common cause of this condition is a deficiency of vitamin B12. This may be due to a dietary deficiency, malabsorption in the terminal ileum, lack of intrinsic factor secreted from gastric parietal cells, or low gastric pH inhibiting attachment of intrinsic factor to ileal receptors.Vitamin E deficiency, which is associated with malabsorption disorders such as cystic fibrosis and Bassen-Kornzweig syndrome, can cause a similar presentation due to the degeneration of the dorsal columns. Diagnosis
Serum vitamin B12, methylmalonic acid, Schilling test, and a complete blood count, looking for megaloblastic anemia if there is also folic acid deficiency or macrocytic anemia. The Schilling test is no longer available in most areas.MRI-T2 images may reveal increased signal within the white matter of the spinal cord, predominantly in the posterior columns and possibly in the spinothalamic tracts. Treatment
Therapy with vitamin B12 results in partial to full recovery where SACD has been caused by vitamin B12 deficiency, depending on the duration and extent of neurodegeneration. References


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