The Effect of Microgravity on Parathyroid Hormone Secretion: A Meta-Analysis
Bibliographic record
Abstract
Background: The relationship between microgravity and parathyroid hormone (PTH), a keystone of bone mineral density, remains controversial. Bone loss is a prominent, ongoing issue in spaceflight, and PTH has been suggested as a treatment for microgravity-induced osteopenia, indicating the importance of this hormone. This systematic review and meta-analysis aimed to evaluate the association between exposure to microgravity and the production of PTH. Methods: PubMed, Embase, Scopus, and Google Scholar were searched for studies reporting PTH levels during and after exposure to microgravity. Non-peer-reviewed articles, studies lacking control groups, and articles published earlier than 2002 were excluded. Twelve articles from 2002 to present, with a total of 145 subjects, were identified and the standardized mean differences from baseline PTH levels were combined in a random effects model. Two-way analysis of variance (ANOVA) with Tukey honestly significant difference (HSD) testing on weighted mean differences was conducted to obtain 95% confidence intervals. Results: Compared to baseline measurements, significant changes in PTH levels are found during and after microgravity exposure. In-flight levels significantly decrease (P < 0.01), and post-flight levels show increases. Furthermore, there is evidence of an interaction between experimental condition (real or simulated microgravity) and time after removal from microgravity on PTH. Conclusions: The findings of this systematic review and meta-analysis suggest that microgravity affects parathyroid gland function during and after spaceflight, with decreases in function in-flight and an increase at 7 days post-flight. Experimental condition also appears to play a role in the recovery timeline of PTH. J Endocrinol Metab. 2023;13(1):1-12 doi: https://doi.org/10.14740/jem849
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".