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we report a case where incidental 18-fluorodeoxyglucose ( 18-fdg ) uptake in pituitary fossa was noted in positron emission tomography - computed tomography ( pet - ct ) , which on further investigations was found to be clinically occult follicle stimulating hormone ( fsh ) secreting pituitary macroadenoma .
a 73-year - old man , known case of hodgkin 's lymphoma , underwent 18-fdg pet - ct for post - chemotherapy evaluation of the disease status .
the scan revealed focal increased fdg uptake in pituitary fossa [ figure 1a and b ] .
the sagittal reformatted ct image [ figure 2a ] showed homogenously enhancing pituitary lesion causing expansion of the sella , and axial contrast ct image [ figure 2b ] showed mildly enhancing rounded lesion in the sella abutting the tuberculum and dorsum sella anteriorly and posteriorly .
( a and b ) fdg pet images showing focal increased fdg uptake in the pituitary fossa ( a and b ) ct images demonstrating mildly enhancing rounded lesion in the sella nuclear magnetic resonance ( nmr ) imaging of brain confirmed the presence of pituitary macroadenoma .
high - resolution , t1-weighted , contrast - enhanced , fat - suppressed sagittal image [ figure 3a ] showed the pituitary lesion , with expanded sella pushing the optic chiasma superiorly , and high - resolution , t1-weighted , contrast - enhanced , fat - suppressed axial image [ figure 3b ] showed homogenously enhancing sellar lesion abutting the cavernous segment of bilateral internal carotid arteries . hormonal assay of the patient showed raised fsh level of 18 iu / ml ( normal range for males up to 5 iu / ml ) .
fat - suppressed sagittal nmr image ( a ) showing pituitary lesion with expanded sella pushing the optic chiasma superiorly and high - resolution , t1-weighted , contrast - enhanced , fat - suppressed axial image ( b ) showing enhancing sellar lesion
a study revealed that the incidence of focally increased fdg uptake in pituitary is only 0.073% .
the mean suvmax calculated without correction for partial volume effect for macroadenomas is reported to be significantly higher than the suvmax for microadenomas .
pituitary adenomas are the most common cause of pituitary hormone hypersecretion and hyposecretion syndromes in adults .
isolated gonadotropin secreting pituitary adenoma with increased levels of circulating fsh , as in our case , is a very rare occurrence .
our case demonstrates the importance of further evaluations , including hormone assays and nmr imaging of the pituitary , to diagnose clinically occult pituitary adenoma when incidental increased pituitary fdg uptake is noted .
a 73-year - old man , known case of hodgkin 's lymphoma , underwent 18-fluorodeoxyglucose positron emission tomography - computed tomography ( 18-fdg pet - ct ) for post - chemotherapy evaluation of the disease status . 
 the scan revealed focal increased fdg uptake in pituitary fossa . 
 the ct images showed homogenously enhancing pituitary lesion causing expansion of the sella . a possibility for the presence of pituitary adenoma 
 was raised in the report . 
 hormonal assay of the patient showed raised follicle stimulating hormone ( fsh ) level of 18 iu / ml ( normal range for males up to 5 iu / ml ) . 
 all the other pituitary hormones were within the normal range . 
 nuclear magnetic resonance ( nmr ) imaging of brain showed a pituitary lesion with expanded sella pushing the optic chiasma superiorly . 
 nmr findings confirmed the presence of pituitary macroadenoma . a final diagnosis of fsh secreting pituitary macroadenoma was made .