Case summary: Thanks to our favorite R3/intern centaur Daniel Kwon, who presented the case of a 60M with PMH HIV on ARVs who presented with dyspnea due to a viral pneumonia and was found to have adrenal insufficiency due to ritonavir potentiation of inhaled nasal steroids!
- In evaluating a patient with hypoglycemia, ensure you confirm Whipple’s triad: 1) hypoglycemia is not a lab error (repeat FSBG and ensure it correlates with serum glucose on a Chem panel), 2) the patient has symptoms of hypoglycemia while hypoglycemic, 3) the patient’s symptoms are relieved with reversal. Finally, if you’re entertaining the diagnosis of insulinoma, ensure you draw the labs for work-up (e.g. C peptide) while the patient is hypoglycemic.
- VA hospitalist and medical educator extraordinaire Denise Connor wrote up a fantastic case in JAMA IM reviewing causes of false FSBG readings, which range from shock and PVD to Waldenstrom’s macroglobinemia.
- Ritonavir and other CYP450 inhibitors can potentiate the action of steroids that are not typically systemically active (topical, inhaled, nasal) and lead to adrenal insufficiency and iatrogenic Cushing’s syndrome.
- Urine studies in hyponatremia due to adrenal insufficiency mimic SIADH (see mechanism below, and thanks to Renal attending Naomi Anker for the teaching!).
“Pseudohypoglycemia”: When FSBG readings don’t reflect serum [glucose]
- Type 1: FSBGs accurately reflect glucose levels in the microcirculation, but are considerably lower than the systemic plasma glucose owing to sluggish capillary blood flow.
- peripheral vascular disease
- cyanotic heart disease
- Raynaud phenomenon
- Type 2: in vitro glycolysis in the collection tube
- Waldenström macroglobulinemia
Here is the fantastic Teachable Moment case on pseudohypoglycemia from Denise Connor et al.: Wang EY, Patrick L, Connor D. Blind Obedience and an Unnecessary Workup for Hypoglycemia: A Teachable Moment. JAMA Intern Med. 2018 Feb 01; 178(2):279-280.
Here is a review of protease inhibitor-mediated potentiation of nasal/inhaled steroids: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3758391/
What causes hyponatremia in adrenal insufficiency?
- Big picture: low cortisol–> CRH–> ADH–> hyponatremia
- Urine studies therefore are indistinguishable from SIADH
We like the Endocrine society breakdown for classifying causes of hypoglycemia: ill/medicated or well
- Drugs (insulin, secretagogues, adulterated illicit drugs, alcohol, lots of prescription meds)
- Critical illness (hepatic, renal, cardiac failure; sepsis)
- Hormone deficiency (adrenal insufficiency)
- Other rare disorders (functional beta cell disorders from other pancreatic tumors or post-gastric bypass, insulin autoimmune hypoglycemia)
- Accidental or surreptitious insulin/secretagogue ingestion
This month’s Podcast of the Month is from Primary Care Perspectives.
In a 30 minute podcast Kate Wallis (Developmental and Behavioural Paediatrician, Children’s Hospital of Philadelphia) discusses the pros and cons of the M-CHAT when screening for autism in the primary care setting. She also shares some helpful tips for picky eaters.
Is the M-CHAT a useful screening tool for non-pervasive developmental disorders?
If you only line up one podcast this month, make it this one.
Listen to the podcast.
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