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