ABSTRACT
OBJECTIVE: To determine if improved delineation of hypothalamic-pituitary neuroanatomy by magnetic resonance imaging, especially the posterior pituitary hyperintense T1 signal, can be correlated with anterior and posterior pituitary endocrine function. DESIGN: Children with ectopic posterior pituitary tissue were identified at the Endocrine Clinic of the Children's Hospital of Pittsburgh (Pa) and their records were reviewed. PARTICIPANTS: Ten children with ectopic posterior pituitary tissue. MEASUREMENTS: Anterior pituitary hormone status, determined by standard testing, was correlated with the morphologic anomalies of the hypothalamic-pituitary region on magnetic resonance imaging. RESULTS: Patients were categorized by the appearance of the pituitary stalk based on the magnetic resonance image: attenuation of the stalk (group 1) or nonvisualization of the stalk (group 2). Patients in group 1 retained partial anterior pituitary function. Patients in group 2 had panhypopituitarism. CONCLUSION: Prospective evaluation of affected individuals may provide insight into the pathophysiologic mechanisms of idiopathic hypopituitarism.
Subject(s)
Choristoma/diagnosis , Hypothalamic Neoplasms/diagnosis , Magnetic Resonance Imaging , Pituitary Gland, Posterior , Adolescent , Child , Child, Preschool , Choristoma/complications , Choristoma/metabolism , Female , Growth Hormone/metabolism , Humans , Hypopituitarism/etiology , Hypopituitarism/metabolism , Hypothalamic Neoplasms/complications , Hypothalamic Neoplasms/metabolism , Hypothalamus, Middle , Infant , Infant, Newborn , Male , Pituitary Diseases/etiology , Pituitary Diseases/metabolism , Pituitary Gland, AnteriorABSTRACT
Section of the neurohypophyseal stalk classically produces a triphasic response: diabetes insipidus (1st phase), hyponatremia or normonatremia (2nd phase), and diabetes insipidus (3rd phase). Transient hyponatremia without diabetes insipidus has been reported after transsphenoidal pituitary surgery. We report two additional cases of transient hyponatremia which occurred 6-8 days after pituitary surgery. We hypothesize that this outcome may be due to partial section or damage of the hypothalamiconeurohypophyseal tracts. The remaining intact vasopressin neurons function normally to protect against the diabetes insipidus of the first and third phase, but leak of vasopressin from the damaged tracts and posterior pituitary is sufficient to cause what can be described as an isolated second phase. To study this hypothesis in rats, partial damage to the hypothalamicneurohypophyseal tracts was produced by radiofrequency lesions. The lesions did not affect anterior pituitary function. A variety of responses in posterior pituitary function occurred, including classic triphasic response in 2 rats and transient hyponatremia in 20 of 35 lesioned animals. The mean sodium nadir was 128.7 +/- 1.5 mEq/l in comparison to the sham-operated value of 140.0 +/- 0.4 mEq/l. Of the 20 rats exhibiting transient hyponatremia, 12 went on to develop diabetes insipidus, and 8 recovered. In the recovered group, the transient hyponatremia occurred 1-3 days after lesioning and returned to normal by day 7 which corresponds to the timing of the second phase of the triphasic response in rats. Hyponatremia was accompanied by vasopressin levels inappropriate for the plasma sodium level, inappropriately concentrated urine, water retention, and natriuresis.(ABSTRACT TRUNCATED AT 250 WORDS)
