(13) and describes relief of the total suppressed PTH secretion from healthy glands after adenectomy. In this model (Fig.
(13) used a preoperative baseline PTH concentration (instead of a true [c.sub.0]); [c.sub.1] and [c.sub.2] were the concentrations 5 and 10 min after adenectomy. Briefly, k (Eq.
where [C.sub.m0] is the PTH concentration at adenectomy.
The decay constant was k = -a', and the approximated PTH concentration at adenectomy was [C.sub.0app = e.sup.b'].
Use of the PTH at adenectomy instead of the preoperative baseline led to lower residual concentrations (significant for DPC and Roche) and significantly longer half-lives with all assays (mean, 1.8 vs 3.7 min).
The time intervals between starting anesthesia and adenectomy ranged from 20 to 77 min, and the average preparation time of the adenoma was 38 min.
Interestingly, up to one-half of the patients with a decrease in PTH during adenoma preparation (n = 14) already exhibited a PTH <50% of the preoperative baseline value at the time of adenectomy (Table 2).
Model A describes fast relief of healthy glands from total PTH suppression after adenectomy because of an unconfirmed assumption that the relief mathematically depends on the same rate constant (k) as the adenomatous PTH decay.
This model could not be used in cases without uniform decreases in PTH, e.g., in most patients with a PTH surge until adenectomy (see footnote a to Table 1).
During minimally invasive parathyroidectomy, the manipulations by the surgeon influence the PTH concentrations until adenectomy (Fig.
A major clinical question that presents itself is the problem as to which PTH concentration, either PTH at adenectomy or preoperative baseline, should be used for reference when calculating the 50% decrease within 10 min.
The decrease in PTH from the preoperative baseline to adenectomy indicates that the vessels of the affected gland have indeed been clamped before excision.