Magnetic resonance imaging of the hypothalamic-pituitary axis in the diagnosis of growth hormone deficiency

In order to investigate the relationship between pituitary appearance and t he 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 possib le GH disorders. On the basis of pituitary function tests, patients were di vided into GPI deficient (GH peak > 15 mIU/I [5.8 ng/ml]) (n = 82) or GH su fficient (GH peak > 15 mIU/I) (n = 28). The former were further divided int o those with multiple hormone deficits (MPHD) (n = 19) or isolated GHD - se vere IGHD (peak GH < 8 mIU/l [3.1 ng/ml]) or partial IGHD (8-15 mIU/I). The appearance of the hypothalamic-pituitary (H-P) axis n as classified as: (1 ) normal, (2) isolated hypoplastic stalk (HPS), (3) isolated hypoplastic an terior lobe (HPAL) (PHT SDS > -2.0), (4) HBS + HPAL or (5) ectopic posterio r lobe (EPL). The last two were considered severe abnormalities. PHT SDS (m ean +/- 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). S ixty-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 GI-I sufficient grou p also had an abnormality (3 severe, but none with an EPL). All patients wi th MPHD had a MRI abnormality, most commonly an EPL (79%). Thus the presenc e of any MRI abnormality as a marker for GHD would generate a sensitivity o f 79%, but a specificity of only 54%, indicating that this could not be use d to confirm GHD. However, the presence of either an EPL or HPS + HPAL on M RI is highly specific (100% and 89% respectively) and predictive of GHD (po sitive predictive value 100% and 79% respectively), indicating that these a bnormalities provide confirmation of the diagnosis. We recommend that if cl inical, auxological and biochemical data indicate a diagnosis of GHD, then a MRT scan should be undertaken to define the pituitary anatomy and to help confirm the diagnosis.