Could GH deficiency unmask Insulinoma?
Vakilgilani T, Tanday R, Woods D, Falinska A, Ling Y, Todd JF , Goldstone AJP
A 53 year old retired military soldier had a 9 months history of recurrent blackouts predominately associated with blurred vision, feeling shaky, sweaty and they were mainly before meals. His past medical history included asthma, multiple shrapnel injuries, hearing impairment secondary to blast injury and chronic back pain with previous surgery. He was on atorvastatin, omeprazole and inhalers.
He was admitted acutely to his local hospital and blood glucose 0.6 mmol/L was found on arrival. Prolonged 72 hour fast was performed which showed an elevated
C-peptide and insulin in the context of hypoglycaemia and negative sulfonylurea (SU) screen consistent with a diagnosis of insulinoma. Subsequent CT abdomen revealed a 14 mm hypervascular lesion within the body of the pancreas consistent with a neuroendocrine tumour. He was then referred to our outpatient Endocrine clinic.
He experienced the above symptoms with normal capillary blood glucose (CBG) in clinic but was admitted for completion of investigations. He had a normal EEG and CT brain. Repeat prolonged fasting confirmed hypoglycaemia with blood glucose of 1.7 mmol/L at 52 hours with inappropriately elevated C-peptide of 1396pmol/L and insulin of 21.6 mU/L and negative SU screen. In addition, concomitant plasma GH of 1.93ug/L (inappropriately low in context of hypoglycaemia) but normal cortisol of 651 nmol/L. LH, FSH and testosterone were 3 iu/L(2-12), 3.3 iu/L(1.7-8) and 6.9 nmol/L(10-30) respectively which is suggestive of secondary hypogonadism. The reminder of a pituitary profile was normal.
Gallium 68 DOTATATE PET CT scan confirmed gallium avid lesion in the body of the pancreas and EUS also confirmed a lesion consistent with an insulinoma.
He is currently waiting for formal ITT to confirm GH deficiency and has commenced testosterone replacement. He has been referred to surgeons for laparoscopic resection of the lesion.
In this case previous blast injury could be the cause of secondary hypogonadism and GH deficiency. It raises the possibility that elimination of GH counter-regulatory action in hypoglycaemia could have unmasked insulinoma.