Pituitary Antibodies in an Adolescent with Secondary Adrenal Insufficiency and Turner Syndrome

Autoimmune hypophysitis (AH) is a rare inflammatory disease of the pituitary gland causing varying degrees of hypopituitarism and/or sellar compression. Cranial MRI remains the best noninvasive tool to diagnose AH, although a diagnosis of certainty requires pituitary biopsy. The objective of this study was to assess the utility of detecting pituitary antibodies for the diagnosis of AH.

A 15-year-old female with Turner syndrome (TS), hypothyroidism, and ovarian failure presented acutely with hypocortisolism. Laboratory studies revealed secondary adrenal insufficiency. MRI showed a hypotrophic pituitary gland and loss of the posterior pituitary bright spot. To establish an autoimmune basis for the adrenal insufficiency, serum was analyzed by double indirect immunofluorescence for the presence of pituitary autoantibodies.

The patient's serum contained autoantibodies that recognized 36% of the adrenocorticotropic hormone-secreting cells, suggesting that these adenohypophyseal cells were targeted by autoimmunity. The serum contained antibodies that identified the majority of the gonadotropin-secreting cells (FSH 77%, LH 65%). No recognition of GH-, prolactin-, and TSH-secreting cells was found. Preabsorption experiments showed that antigenic targets of autoantibodies were not anterior pituitary hormones themselves.

Demonstration of circulating pituitary antibodies expands the diagnostic options for AH. In this adolescent with TS, positive and cell-specific pituitary antibodies suggested that AH was the cause of her secondary adrenal insufficiency.