Neuroendocrine Case 2

A 45-year-old man who underwent transsphenoidal resection of a clinically non-functioning pituitary macroadenoma 6 months ago returns for endocrine follow-up. He says that his stamina and overall well-being have diminished since he underwent pituitary surgery. He has gained 10 lb postoperatively. He reports no headache, visual symptoms, nausea, constipation, dizziness, polyuria, low libido, erectile dysfunction, edema. His past medical history is otherwise significant for gastro-esophageal reflux disease but no diabetes mellitus or malignancy. His only medication includes omeprazole 20 mg daily. On examination, he appears well. His blood pressure is 125/84 mm Hg and his pulse is 78 / min. His weight is 210 lb with a height of 5’7” (body mass index: 32.7 kg/m2). There are no features of acromegaly or Cushing’s on exam. Visual fields are full on confrontation testing. There is no goiter. Muscle strength is intact. 

A recent postoperative MRI examination shows anticipated postoperative findings and a small tumor remnant (measuring 3 mm by 3 mm by 4 mm) present in the right cavernous sinus. 

Recent laboratory tests include: prolactin: 10 ng/ml (normal, 0 to 23); IGF-I: 95 ng/ml (normal, 50 to 320); TSH: 2.5 mcu/ml (normal, 0.4 to 4.5); free T4: 1.2 ng/dl (normal, 0.8 to 1.8); ACTH: 22 pg/ml (normal, 5 to 60); morning cortisol: 18.2 mcg/dl; LH: 2.1 U/l (normal, 1 to 8); FSH: 3.4 U/l (normal, 1 to 8); total testosterone: 420 ng/dl (normal, 250 to 800). 

He undergoes a glucagon stimulation test, during which his growth hormone reaches a peak level of 2.1 ng/ml. 

Question 1

How would you interpret these data and approach this patient’s endocrine management? 

A. Based on the result of the glucagon stimulation test, the patient has documented growth hormone deficiency and may begin a trial of growth hormone replacement.
B. This patient’s serum IGF-I level is within the normal range; therefore, he does not have growth hormone deficiency.
C. The results of the glucagon stimulation test suggest the presence of growth hormone deficiency but the presence of residual adenoma is a contraindication to growth hormone replacement.
D. This patient’s growth hormone response to glucagon stimulation is normal; therefore, growth hormone replacement is not indicated.
E. This patient’s serum IGF-I level is normal but his growth hormone response to glucagon stimulation is abnormally low; in light of the discrepancy, he should undergo a different growth hormone stimulation test in order to establish the diagnosis of grow
Incorrect!
Correct!
Correct Answer
D. This patient’s growth hormone response to glucagon stimulation is normal; therefore, growth hormone replacement is not indicated.

This patient is at risk for growth hormone deficiency in light of his history of pituitary macroadenoma and transsphenoidal pituitary surgery. His presentation has reasonably raised concerns for possible pituitary dysfunction. His thyroid, adrenal and gonadal axes are intact based on available data. However, the presence of obesity is associated with decreased growth hormone response to glucagon stimulation testing in healthy adults. In this patient, the peak growth hormone response to glucagon stimulation is normal (>1 ng/ml) taking obesity into account. Therefore, there is no indication for growth hormone replacement in this case (answer D is correct and answers A, C and E are incorrect). If the patient was lean, then a growth hormone cutpoint of 3 ng/ml would be appropriate to establish the diagnosis of growth hormone deficiency based on the result of the glucagon stimulation test. The presence of a small residual adenoma is not a contraindication for growth hormone replacement (answer C is incorrect). Available data suggest that growth hormone replacement does not increase the risk of progression of pituitary adenomas. However, regular periodic imaging of the sella would be advisable as part of good clinical practice. In adults with growth hormone deficiency, serum IGF-I levels are often within the normal reference range (albeit in the lower half of the range). Therefore, a normal serum IGF-I level does not exclude the possibility of growth hormone deficiency in this patient (answers B and E are incorrect).  

 

Reference: 

  1. Yuen KCJ, et al. American Association of Clinical Endocrinologists and American College of Endocrinology guidelines for management of growth hormone deficiency in adults and patients transitioning from pediatric to adult care. Endocrine Practice. 2019;25(11):1191-1232. 

This patient is at risk for growth hormone deficiency in light of his history of pituitary macroadenoma and transsphenoidal pituitary surgery. His presentation has reasonably raised concerns for possible pituitary dysfunction. His thyroid, adrenal and gonadal axes are intact based on available data. However, the presence of obesity is associated with decreased growth hormone response to glucagon stimulation testing in healthy adults. In this patient, the peak growth hormone response to glucagon stimulation is normal (>1 ng/ml) taking obesity into account. Therefore, there is no indication for growth hormone replacement in this case (answer D is correct and answers A, C and E are incorrect). If the patient was lean, then a growth hormone cutpoint of 3 ng/ml would be appropriate to establish the diagnosis of growth hormone deficiency based on the result of the glucagon stimulation test. The presence of a small residual adenoma is not a contraindication for growth hormone replacement (answer C is incorrect). Available data suggest that growth hormone replacement does not increase the risk of progression of pituitary adenomas. However, regular periodic imaging of the sella would be advisable as part of good clinical practice. In adults with growth hormone deficiency, serum IGF-I levels are often within the normal reference range (albeit in the lower half of the range). Therefore, a normal serum IGF-I level does not exclude the possibility of growth hormone deficiency in this patient (answers B and E are incorrect).  

 

Reference: 

  1. Yuen KCJ, et al. American Association of Clinical Endocrinologists and American College of Endocrinology guidelines for management of growth hormone deficiency in adults and patients transitioning from pediatric to adult care. Endocrine Practice. 2019;25(11):1191-1232.