Endocrine Abstracts

Introduction: Short synacthan test is a first line endocrine test for diagnosing adrenal insufficiency except in situations like Pituitary surgery or Pituitary apoplexy within the last 2 weeks when this may give a false positive result and this is well known in literature. Here we discuss lesser reported clinical situations seen in two of our patients having good adrenal response to SST with only GST identifying adrenal insufficiency.

Case Report: Two patients who were seen in Endocrine out patients clinic. Patient A has symptoms of hypogonadism and feeling generally tired all the time. Morning cortisol was low with slightly raised prolactin levels but other anterior pituitary hormones and MRI pituitary were normal. SST showed low 0 min cortisol but satisfactory 30 minute response. Because of low 0 min cortisol and ongoing symptoms of tiredness, GST was performed which confirmed adrenal insufficiency. Patient B presented with hyponatraemia. Her Anterior pituitary test were all normal except low morning cortisol. Her MRI Pituitary showed Pituitary Macroadenoma. CT thorax, abd, pelvis was normal. SST showed good 30 minute response. She was symptomatic with low sodium, therefore GST was performed, which confirmed adrenal insufficiency

Discussion: The cause of adrenal insufficiency in both these cases were inadequate release of ACTH from the Anterior Pituitary gland when challenged with GST. Potential mechanisms involving the satisfactory 30 minute cortisol with SST are likely these patients may be in the initial phase of pan hypopituitarism and were secreting ACTH just enough to meet the daily requirement but not enough to stimulate adrenals during the time of stress or illness.

Conclusion: These cases highlights the importance of GST in detecting adrenal insufficiency under stress. Interpreting SST on the basis of 30mins cortisol response alone may mask borderline adrenal insufficiency as SST does not test the whole pituitary adrenal axis.