Serum calcitonin forms and concentrations in young and elderly healthy females

What matters in aging is signaling for responsiveness

Biological responsiveness refers to the capacity of living organisms to adapt to changes in both their internal and external environments through physiological and behavioral mechanisms. One of the prominent aspects of aging is the decline in this responsiveness, which can lead to a deterioration in the processes required for maintenance, survival, and growth. The vital link between physiological responsiveness and the essential life processes lies within the signaling systems. To devise effective strategies for controlling the aging process, a comprehensive reevaluation of this connecting loop is imperative. This review aims to explore the impact of aging on signaling systems responsible for responsiveness and introduce a novel perspective on intervening in the aging process by restoring the compromised responsiveness. These innovative mechanistic approaches for modulating altered responsiveness hold the potential to illuminate the development of action plans aimed at controlling the aging process and treating age-related disorders.

EFFECT OF AGE AND GENDER ON FASTING AND FOOD-STIMULATED LEVELS OF CALCITONIN, PARATHYROID, AND GASTRIN HORMONES IN HEALTHY ADULTS

Objective: To investigate the effect of age and gender on basal and food-stimulated serum calcitonin (CT), parathyroid hormone (PTH), and gastrin levels among healthy adults. Methods: Ninety-six healthy adults (76 men and 20 women) aged between 21 and 43 years were recruited. Serum CT, PTH, and gastrin levels were measured after a 9-hour overnight fast, and 1 and 3 hours postprandially. Results: PTH levels decreased early and increased late after feeding. This change was significant in men but not in women. CT levels increased in response to food intake in men but not in women. Gastrin levels were significantly increased after feeding in both men and women. Mean basal and food stimulated CT, PTH, and gastrin levels did not significantly differ between genders. Fasting and post-prandial PTH levels were higher while gastrin levels were lower in older subjects (>30 years old) compared to younger subjects (≤30 years old). Fasting and postprandial CT levels were not significantly different between age groups. Conclusion: Age had a significant effect on fasting and food-stimulated PTH and gastrin hormone levels. The effect of age on PTH levels was independent of baseline vitamin D levels. Men showed significant changes in CT and PTH levels in response to feeding compared to women, although the mean hormone levels were not significantly different between men and women. Abbreviations: CT = calcitonin; MTC = medullary thyroid carcinoma; PTH = parathyroid hormone; SD = standard deviation.

Should food intake and circadian rhythm be considered when measuring serum calcitonin level?

OBJECTIVE

To investigate the relationship between both food intake and circadian rhythmicity and serum calcitonin in the same individuals.

METHODS

Eighteen healthy subjects, 10 males and 8 females, aged 22 to 24 years, were recruited. Serum calcitonin level was measured three times: at 0800 after a 9-hour overnight fast, at 0900 postprandially, and at 1700 after another 9-hour fast. The same protocol was repeated once.

RESULTS

The mean calcitonin levels (at 0800) were 3.92 pg/mL (SD, 2.5 pg/mL) on Day 1 and 3.52 pg/mL (SD, 2.1 pg/mL) on Day 2. Mean postprandial calcitonin (at 0900) was 9.46 pg/mL (SD, 8.6 pg/mL) on Day 1 and 9.91 pg/mL (SD, 6.9 pg/mL) on Day 2. Mean fasting calcitonin in the evening (at 1700) was 6.74 pg/mL (SD, 4.73 pg/mL) on Day 1 and 6.49 pg/mL (SD, 3.57 pg/mL) on Day 2. There was no significant difference in the mean calcitonin level on days 1 and 2 for any of the three time points examined. Statistically significant differences were found between postprandial and evening calcitonin levels and the fasting levels on Day 1 (P = .018 and .015, respectively) and Day 2 (P = .001 and .0009, respectively).

CONCLUSION

These results suggest that serum calcitonin level is significantly influenced by food intake in healthy young subjects and reveal a circadian rhythm, with increased calcitonin level during the afternoon. The timing of blood sampling relative to meals should be integrated into clinical practice and research settings involving serum calcitonin measurements.

Measurement of calcitonin by immunoassay analyzers

BACKGROUND

Since Nichols Institute Diagnostics (NID) ended production of their automated calcitonin immunoassay, evaluation of an alternative calcitonin assay was necessary.

METHODS

Calcitonin measured by the NID procedure was compared with a test from Diagnostic Products Corporation (DPC). Calcitonin was also measured by assays from DiaSorin (DS) and Scantibodies (SC).

RESULTS

In 187 samples, detection failed either by NID (39%) or DPC (96%) assay; in 35% of samples, the tests agreed for non-measurable calcitonin. The regression line DPC=0.78 x NID-0.3 (r=0.998) fitted results from 236 samples with detectable calcitonin. A linear relationship, albeit with scattering at low concentrations, was observed. Importantly, stimulation by pentagastrin above basal calcitonin concentrations yielded similar results with both assays. Comparisons (DPC=0.80 x DS-3.4 and DPC=0.81 x SC-1.1) confirmed an aberrant calibration of the DPC test. To overcome the method bias, we propose a multiplication factor of 0.8 to convert NID to DPC results.

CONCLUSIONS

Apparently due to non-specific effects, the DS and SC assays produced calcitonin results in samples from completely thyroidectomized patients, while the DPC assay correctly failed to detect calcitonin. Thus, the DPC assay on an Immulite 2000 analyzer may be used as a more accurate substitute for NID if the different calibration is noted.

Calcitonin gene-related peptide and calcitonin in the CSF of patients with dementia and depression: possible disease markers

Cerebrospinal fluid (CSF) was obtained from 32 patients with dementia, 19 healthy controls that were age-matched with the dementia patients, and 29 DSM-IV major depression patients and calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) and calcitonin-like immunoreactivity (CT-LI) measured by RIA. CGRP-LI was lower in the dementia group compared to both the controls and depressed patients (P<.01) after covarying out sex and age. CT-LI was decreased in the dementia and depressed patients (P<.05) compared to the controls. A positive relationship between CGRP-LI and CT-LI was found in dementia. A logistic discriminant analysis with calcitonin gene-related peptide (CGRP) and log calcitonin (CT) predicting diagnosis (three classes) revealed a significant overall fit (chi2 = 18.08, P = .0011), with an effect test showing contributions of both independent variables: CGRP (chi2 = 10.03, P<.007), log CT (chi2 = 8.63, P = .013). In dementia, both CGRP-LI and CT-LI were decreased and their concentration ratio did not differ from that in controls, likely reflecting a general neuronal loss. Alternatively and more speculatively, but theoretically possible, expression of the alpha-CGRP/CT gene may be affected in dementia. In contrast, in depression, CT-LI but not CGRP-LI was decreased and the CGRP/CT concentration ratio was increased, which is consistent with a possibility of an altered splicing process favoring CGRP mRNA.

Circulating monomer-like calcitonin in osteoporotic patients

Physiological concentrations of monomeric calcitonin can inhibit osteoclastic bone resorption in vitro. We therefore investigated the circulating molecular forms, including monomer-like calcitonin, and their concentrations in 9 men and 9 women with established osteoporosis. Calcitonin was immunoextracted from serum by the use of rabbit calcitonin antibodies coupled to Sepharose 4B. The lyophilized extracts were incubated with 6 M urea overnight and gel chromatographed in a fast protein liquid chromatography (FPLC) system; calcitonin was measured by radioimmunoassay in the fractions. FPLC disclosed immunoreactive calcitonin of three different molecular sizes in the patients. The two largest forms were approximately 30 and 10 kDa and one eluted at the same position as monomeric calcitonin (3.4 kDa). After extraction and FPLC we found slightly higher calcitonin concentrations in osteoporotic women than previously reported levels in age-matched healthy women. Male patients had higher levels than female patients. None of the osteoporotic patients lacked monomer-like calcitonin. There was no significant correlation between the extracted total or monomer-like calcitonin and bone mineral density of the femoral neck. It is concluded that the circulating calcitonin in both male and female patients comprises three different molecular forms and that there is no deficiency of the monomer-like form. The calcitonin levels in the female patients were slightly higher than in a previous control group.