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"The only thing that all of the people with APS Type 1 have in common is the will to survive" -- Pablo Ramírez

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My 22yo son has had episodes (once a year since he was 15) of severe cramping and fatigue when exercising in the heat. A recent episode at college during a golf class resulted in a trip to the ER via ambulance. His symptoms are those classic of hypocalcemia, however his serum Ca was 9.5 while "contracted" at the ER. CBC, CMP, & UA were normal (urine pH 9.0). He has positive Chvostek and Trousseau signs. An endocrinologist has since tested his PTH & found it low three different times (4,9,16). He has never tested low on serum Ca or ionized Ca. His DHEA-s was low at 90. A cotrosyn stimulation test with the standard 250 dose increased his cortisol from a basal of 17.3 to a peak at 60 minutes of 17.9. (basal ACTH and cortisol levels were normal) His endocrinologist is sending us for a second opinion with an endocrinologist that specializes in parathyroid. What tests need to be done to confirm or rule out PGA-1?

re: diagnostic tests

Posted by dr at January 02, 2008 10:52 AM
APS-1 can be definitively diagnosed from genetic analyses. Happily these are commercially available through the Athena laboratories in Boston. Hypoparathyroidism cannot be supported when the serum calcium levels have been repeatedly normal however. Transient over-breathing or panic hyperventilation is one physiological cause of tetany where the alkalosis induced by the loss of carbon dioxide can reduce the level of ionized or available calcium thereby inducing muscle spasm. One the episode is over, the alkalosis will resolve and the ionized or biologically available portion of calcium with normalize and the tetany resolve. Magnesium deficiency can also result in tetany. On the other hand, the onset of adrenal insufficiency could mask hypoparathyroidism which can become declared when replacement steroids are given. The adrenal studies in the case however appear in aggregate to be normal. Adrenal autoimmunity is hall marked by antibodies to an enz! yme named 21-hydroxylase which is available through commercial laboratories in the US and help exclude this possibility. Antibodies against the calcium sensing receptor have been described in hypoparathyroidism but have only been performed in a research setting. I hope that this information might be helpful.
Kind regards,
Noel Maclaren MD

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