Background: Nadir GH<2 mU/l in OGTT, normal IGF-I and mean GH<5 mU/l in the growth hormone day curve (GHDC) are considered the therapeutic endpoints in patients with acromegaly. However, discrepancies between these parameters have been reported.
Aim: To compare the utility of the above tests in assessing the acromegaly status following surgical treatment.
Patients and methods: Twenty-six consecutive patients (16 females) diagnosed with acromegaly and macroadenoma had OGTT, GHDC and IGF-I measurement 1618 weeks following transsphenoidal adenomatectomy. Data were analysed with appropriate statistical methods.
Results: Among patients with nadir GH<2 mU/l in the OGTT, 83% had mean GH in the OGTT <5. Among those with nadir GH >2 in the OGTT, 63% had mean GH in the OGTT >5. Among subjects with nadir GH <2 in OGTT, 11% had mean GH >5 in GHDC and 0% had high IGF-I. Among those with nadir GH >2 in OGTT, 25% had mean GH <5 in the GHDC and 63% had normal IGF-I. Among patients with mean GH <5 in the GHDC, 0% had high IGF-I and among those with mean GH >5 in the GHDC, 63% had normal IGF-I. Nadir GH <2.14 in OGTT had sensitivity 89%, specificity 75%, positive predictive value (PPV) 89% and negative predictive value (NPV) 75% in predicting GH <5 in the GHDC and sensitivity 78%, specificity 0%, PPV 100% and NPV 38% in predicting normal IGF-I. Mean GH <4.13 in OGTT had sensitivity 89%, specificity 87%, PPV 94% and NPV 78% in predicting GH <5 in GHDC. Mean GH <10 in the OGTT had sensitivity 96%, specificity 100%, PPV 100% and NPV 75% in predicting normal IGF-I.
Conclusions: Reluctantly, in cases of acromegaly following adenomatectomy, the OGTT and the GHDC do not always provide consistent data making both tests necessary for the assessment of the therapeutic result.