MR-IMAGING DIAGNOSIS OF CENTRAL PRECOCIOUS PUBERTY - IMPORTANCE OF CHANGES IN THE SHAPE AND SIZE OF THE PITUITARY-GLAND

OBJECTIVE. Central precocious puberty occurs as a result of premature pituitary stimulation and increased secretion of gonadotropins. The ai ms of this study were to analyze MR imaging findings in the pituitary glands of children with central precocious puberty compared with match ed control subjects, to define MR imaging-derived variables useful in the diagnosis of central precocious puberty, and to correlate MR imagi ng-derived variables with the hormonal profile and other imaging and c linical findings. MATERIALS AND METHODS. Twenty-six children with cent ral precocious puberty (two boys and 24 girls) were divided into two s ubgroups according to MR imaging findings: idiopathic (21 patients) an d nonidiopathic (five patients: three hypothalamic hamartomas, one pin eal tumor, one empty sella syndrome). The control group consisted of 1 7 normal age- and sex-matched children (two boys, 15 girls). Analyzed parameters included pituitary height, length, width, midsagittal cross -sectional area, calculated volume, and shape. The shape was assessed by a pituitary grading system and two other shape indexes (length-to-h eight and length-to-width ratios). Pituitary grade was defined by the concavity of the upper pituitary surface (grade 1 = marked concavity, grade 2 = mild concavity, grade 3 = flat, grade 4 = mild convexity, gr ade 5 = marked convexity). RESULTS. Pituitary grade showed a highly si gnificant difference among groups (p < .001). Area, height, and length -to-height ratio were significantly different (p < .05), whereas lengt h, width, length-to-width ratio, and volume were not. There was no sig nificant difference in any of the variables compared between idiopathi c and nonidiopathic groups. When selected variables (pituitary grade, area, height, length) in the central precocious puberty group were str atified by bone age and findings on pelvic sonograms, patients with ad vanced bone age had a significantly higher pituitary grade (p < .01) a nd had a tendency toward a greater pituitary length. Pituitary size an d shape correlated with the hormonal profile. CONCLUSION. Change in pi tuitary grade is the most helpful variable for the diagnosis of centra l precocious puberty in a prepubertal child. A high pituitary grade (4 or above) is highly predictive of central precocious puberty, with th e highest specificity and positive predictive value, but with low sens itivity. The use of combinations of high pituitary grade with two othe r positive findings (height and area greater than 1 SD from the respec tive means in the control group) improves the sensitivity, specificity , and predictive value of MR imaging in the diagnosis of central preco cious puberty.