In order to determine the possible cause of this condition, participating members of the family were compared to a group of standard phenotype individuals. While most blood serum levels were normal, the researchers noted a large increase in the amount of serum osteocalcin, a marker of bone formation (Boyden, 2002). There was no corresponding increase in osteoclast activity markers, suggesting that the bone wasn't being broken down as quickly as it was being built up.
The condition was eventually traced to a mutation in LRP5, a gene in which a separate mutation is tied to osteoporosis. While the study is fairly old, the mutation itself provides some interesting ethical questions. Humans are not designed to hurtle along in cars going 70 mph, and evolution has not prepared us to do so. Yet this mutation seems to provide a route for us to start surviving those high speed impacts by modifying our bone structure. The mutation seems to have very limited negative effects, so would it be ethical to begin modifying embryos to carry this mutation, as vehicles get faster and faster? It's significantly possible that lives could be saved, but quality of life may change due to the increased weight (the next Michael Phelps will definitely NOT carry this mutation). The ethics of modifying human genes is a massive debate, but this surely ties into it.
Article:
High Bone Density Due to a Mutation in LDL-Receptor–Related Protein 5. (2002). New England Journal of Medicine, 347(12), 943-944. doi:10.1056/nejm200209193471216
What an interesting article! I am surprised that they did not test calcitonin levels in conjunction with levels of parathyroid hormone and vitamin D metabolites. While parathyroid hormone causes an increase in the concentration of calcium in the blood, calcitonin decreases the concentration of calcium in the blood. Although levels of parathyroid hormone and vitamin D metabolites were normal in this study, I think that levels of calcitonin would have also been an indicative and interesting lab result. As we have learned in physiology, regulating different processes in the body requires a balance of stimulating one process and inhibiting the other. For example, increasing heart rate not only requires stimulating the sympathetic division of the autonomic nervous system, but also inhibiting the parasympathetic division of the autonomic nervous system. I think a similar idea applies here. Not only should we be concerned about how much calcium we release into the blood (parathyroid hormone), but we should also be concerned about how much calcium we retain (calcitonin.) This one-two punch is important in calcium homeostasis, hence my surprise that calcitonin levels were not tested.
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