Abstract
In primary hyperparathyroidism (pHPT), a preferential release of intact PTH (i-PTH) versus carboxyl-terminal PTH fragments is known to occur. We studied whether the release of amino-terminal PTH fragments (N-PTH) is also changed. Serum levels of i-PTH and N-PTH were determined under basal conditions and following oral intake of calcium in six patients with pHPT before and immediately after surgery and in seven healthy subjects. In the patients, baseline levels of both i-PTH and N-PTH were increased preoperatively. The increase was larger in i-PTH compared to N-PTH. Therefore, the N/i ratio was reduced compared to healthy subjects (P<0.05). On the first postoperative day, serum i-PTH decreased to a larger extent than N-PTH, which increased the N/i ratio above that in healthy subjects (P< 0.05). On the 5th postoperative day, the N/i ratio was normalized. Preoperatively, the suppressibility of i-PTH calcium was impaired in the patients (P<0.05), whereas the suppressibility of N-PTH was normal, resulting in unchanged N/i ratio during the oral calcium load. In contrast, the N/i ratio increased normally during the calcium load at day 5 postoperatively (P<0.05). We therefore conclude that: (1) in pHPT, circulating PTH immunoheterogeneity is altered with a preferential release of intact PTH compared to N-terminal PTH fragments and this alteration is normalized after surgery, (2) the secretion of intact PTH and N-terminal PTH shows different sensitivity to inhibition by calcium.
Zusammenfassung
Bei primärem Hyperparathyreoidismus (pHPT) kann, wie man weiβß, eine Freisetzung eher von intaktem PTH (i-PTH) als von Fragmenten mit end-ständigen Carboxylgruppen erfolgen. Wir untersuchten, ob die Freisetzung von PTH-Fragmenten mit terminalen Aminogruppen (N-PTH) sich ebenfalls ändert. Es wurden die Serumspiegel von i-PTH und N-PTH unter folgenden Bedingungen bestimmt: (1) bei 6 pHPT-Patienten (a) ohne Kalziumgabe, (b) nach oraler Kalziumgabe vor und unmittelbar nach Operation und (2) bei 7 gesunden Personen. Bei ersteren waren präoperativ beide Spiegel — i-PTH und N-PTH — erhöht, die i-PTH-Spiegel etwas stärker. Daher war das Verhältnis N-PTH/i-PTH im Vergleich zu gesunden Personen vermindert (p<0,05). Postoperativ war am 1. Tag das Serum-i-PTH stärker vermindert als das N-PTH, wodurch das N-PTH/i-PTH-Verhältnis gegenüber Gesunden zunahm (p<0,05); am 5. Tag normalisierte sich dieses Verhältnis. Präoperativ verbesserte sich die Supprimierung von i-PTH-Kalzium bei den Patienten, während die Supprimierung von N-PTH-Kalzium normal blieb, was seinen Ausdruck fand in einem unveränderten N-PTH/i-PTH-Verhältnis während der oralen Kalziumeinnahme. Im Gegensatz dazu vergrößerte sich das N-PTH/i-PTH-Verhältnis in normaler Weise während der Kalziumeinnahme am 5. Tag postoperativ (p<0,05). Schlußfolgerungen: (1) Bei pHPT ändert sich die zirkulierende PTH-Immunheterogenität mit einer vorzugsweisen Freisetzung von i-PTH im Vergleich zu N-PTH, und diese Veränderung normalisiert sich nach Operation. (2) Die Sekretion von i-PTH und N-PTH zeigt unterschiedliche Sensitivität gegenüber einer Inhibierung durch Kalzium.
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Bergenfelz, A., Valdermarsson, S. & Ahrén, B. Immunoheterogeneity of parathyroid hormone pre- and postoperatively in primary hyperparathyroidism. Langenbecks Arch Chir 380, 119–124 (1995). https://doi.org/10.1007/BF00186419
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DOI: https://doi.org/10.1007/BF00186419