Magnetic Resonance Imaging of the Hypothalamic-Pituitary Axis in the Diagnosis of Growth Hormone Deficiency

Abstract

In order to investigate the relationship between pituitary appearance and the diagnosis of growth hormone deficiency (GHD), we have assessed magnetic resonance imaging (MRI) scans and GH status during provocation tests in 110 patients (78 males; median age 9.8, range 0.1-20 yr), evaluated for possible GH disorders. On the basis of pituitary function tests, patients were divided into GH deficient (GH peak < 15 mIU/l [5.8 ng/ml]) (n = 82) or GH sufficient (GH peak > 15 mIU/l) (n = 28). The former were further divided into those with multiple hormone deficits (MPHD) (n = 19) or isolated GHD - severe IGHD (peak GH < 8 mIU/l [3.1 ng/ml]) or partial IGHD (8-15 mIU/l). The appearance of the hypothalamic-pituitary (H-P) axis was classified as: (1) normal, (2) isolated hypoplastic stalk (HPS), (3) isolated hypoplastic anterior lobe (HPAL) (PHT SDS < -2.0), (4) HPS + HPAL or (5) ectopic posterior lobe (EPL). The last two were considered severe abnormalities. PHT SDS (mean +/- SD -2.0 +/- 2.2) was correlated to log peak GH levels in the whole group (r = 0.45; p < 0.0001) and in the GHD group (r = 0.39; p < 0.0001). Sixty-five out of 82 in the GHD group had a H-P axis abnormality (45 severe abnormalities), while 13 out of the 28 patients in the GH sufficient group also had an abnormality (3 severe, but none with an EPL). All patients with MPHD had a MRI abnormality, most commonly an EPL (79%). Thus the presence of any MRI abnormality as a marker for GHD would generate a sensitivity of 79%, but a specificity of only 54%, indicating that this could not be used to confirm GHD. However, the presence of either an EPL or HPS + HPAL on MRI is highly specific (100% and 89% respectively) and predictive of GHD (positive predictive value 100% and 79% respectively), indicating that these abnormalities provide confirmation of the diagnosis. We recommend that if clinical, auxological and biochemical data indicate a diagnosis of GHD, then a MRI scan should be undertaken to define the pituitary anatomy and to help confirm the diagnosis.

Investigação neurorradiológica de pacientes com deficiência idiopática de hormônio do crescimento

“…The results found by this study are comparable with published data that also records a large number of morphological anomalies in MRI of the hypothalamic-pituitary area of patients with GHD, among which an ectopic posterior pituitary was common. 4,6,9 One of our patients with short stature and suspected GHD had a normal CT scan, IGF-1 above the minimum for normality (-2 SD), normal growth hormone response to ITT for pubertal stage, making the MRI findings of a hypoplastic anterior pituitary associated with an ectopic posterior pituitary (Figure 1) decisive to GHD diagnosis. Other authors 11,12 also value the abnormalities visible on MRI as being important for differential diagnosis of children with restricted stature, since, in the face of difficulties with establishing normal values and with reproducibility of GH stimulation tests, the presence of structural abnormalities in the hypothalamic-pituitary area of such children, reinforces the possibility of a hormone deficiency.…”

“…Images obtained by MRI offer greater accuracy compared with CT, and MRI is therefore considered a better method than CT for investigating patients with GHD. 5 Recent studies of children with reduced height known to have GHD, resulting from causes other than tumors, demonstrate that the principal abnormality found with MRI is hypoplastic anterior pituitary associated with an interrupted stalk and ectopic posterior pituitary, [1][2][3][4]6 this last being rarely seen with CT. 5 It is, therefore, consensus that when investigating restricted stature, the observation of a hypoplastic anterior pituitary associated with an ectopic posterior pituitary on MRI can be a strong indication of GHD. 1,3,4,11,12 Among our patients, 54% presented abnormalities on MRI and, of the abnormalities observed, a hypoplastic anterior pituitary associated with an ectopic posterior pituitary was the most common finding, being present in 70% of our cases.…”

“…1,4,8 This study is based on the hypothesis that structural abnormalities in the hypothalamic-pituitary region would be common in our group of patients with GHD, and that abnormal MRI findings could be an indicator of hypopituitarism severity. As ectopic posterior pituitary is frequently observed in patients with GH deficiency, 4,6,7 we postulated that if this finding is present in our short stature patients it would allow us to diagnose doubtful cases, thus avoiding unnecessary exhaustive laboratory investigation.…”

“…Previously the majority of GHD cases were diagnosed as idiopathic, but with the advent of MRI it has been possible to observe in such patients a characteristic structural anomaly described as the pituitary stalk interruption syndrome, 3,4,6,7 which is more difficult to identify with CT. 5 A number of different publications 1,3,4,6,8 have tried to correlate the morphological alterations seen with MRI with isolated growth hormone deficiency (IGHD) or as multiple anterior pituitary deficiencies (MPHD). Studies have shown that children with MPHD exhibit a higher frequency of abnormalities on MRI when compared with those that have IGHD.…”

Neuroradiological investigation in patients with idiopathic growth hormone deficiency

“…Anteriormente, a maioria dos casos de DGH era diagnosticada como idiopática; com advento da RM, tem sido possível observar, nesses pacientes, uma anormalidade estrutural característica denominada de síndrome de interrupção da haste hipofisária 3,4,6,7 , a qual, pela TC, é mais difícil de ser identificada 5 . Várias publicações 1,3,4,6,8 tentam correlacionar as alterações morfológicas visualizadas à RM com a deficiência isolada de hormônio do crescimento (DGHI) ou com deficiência de múltiplos hormônios hipofisá-rios (DGHM).…”