Unless you’ve spent time reading medical anatomy texts, the term parathyroid gland probably sounds like a spelling error. But no, we aren’t talking about the thyroid gland, we’re talking about four little glands within that bigger gland. If you don’t believe they exist, here’s the Wiki article and the Britannica article.
So what do these little guys do? They maintain calcium levels in the body. So more parathyroid hormone tends to lead to greater vitamin D absorption. Greater vitamin D means greater calcium absorption. But what happens when there isn’t enough vitamin D? Shouldn’t we all develop high levels of parathyroid hormone (hyperparathyroidism)?
Sometimes we do and sometimes we don’t. Healthy individuals did not develop high levels of parathyroid hormone in the absence of vitamin D. Instead, they had chronic vitamin D deficiencies and the parathyroid evidently thought it was easier to get the extra calcium from the bone. In older patients who’d had a hip fracture, far more men got high levels of parathyroid hormone than women. So something is going on that prevents our bodies from responding adequately to vitamin D deficiency.
Rather than trying to solve osteoporosis with drugs, shouldn’t we be spending more time researching how to restart the parathyroid hormone in deficient individuals?
J Nutr Health Aging. 2013 Feb;17(2):180-4. doi: 10.1007/s12603-012-0088-y.
Parathyroid hormone response to severe vitamin D deficiency is sex associated: an observational study of 571 hip fracture inpatients.
Di Monaco M, Castiglioni C, Vallero F, Di Monaco R, Tappero R.
Osteoporosis Research Center, Division of Physical Medicine and Rehabilitation, Presidio Sanitario San Camillo, Torino, Italy. firstname.lastname@example.org
To investigate the association between sex and parathyroid hormone response to severe vitamin D deficiency after hip fracture.
Rehabilitation hospital in Italy.
571 consecutive inpatients with hip fracture and severe vitamin D deficiency (serum 25-hydroxyvitamin D < 12ng/ml), without hypercalcemia or estimated glomerular filtration rate (GFR) < 15ml/min.
In each patient we assessed PTH (by two-site chemiluminescent enzyme-labelled immunometric assay), 25-hydroxyvitamin D (by immunoenzymatic assay), albumin-adjusted total calcium, phosphate, magnesium, and creatinine 21.3 ± 6.1 (mean ± SD) days after fracture occurrence. Functional level was assessed using the Barthel index. PTH response to vitamin D deficiency was classified as either secondary hyperparathyroidism (serum PTH >75pg/ml) or functional hypoparathyroidism, i.e., inappropriate normal levels of PTH (≤75pg/ml).
Among the 571 patients, 336 (59%) had functional hypoparathyroidism, whereas 235 (41%) had secondary hyperparathyroidism. PTH status was significantly different between sexes (p=0.003): we found functional hypoparathyroidism in 61% of women and 43% of men (secondary hyperparathyroidism in 39% of women and 57% of men). The significance of the between-sex difference was maintained after adjustment for age, estimated GFR, phosphate, albumin-adjusted total calcium, albumin, Barthel index scores, 25-hydroxyvitamin D, and hip fracture type (either cervical or trochanteric). The adjusted odds ratio was 1.85 (95%CI from 1.09 to 3.13; p=0.023).
Data shows that PTH response to vitamin D deficiency was sex-associated following a fracture of the hip. The higher prevalence of secondary hyperparathyroidism may play a role in the known prognostic disadvantage found in hip-fracture men.
Horm Metab Res. 2013 Jan;45(1):43-6. doi: 10.1055/s-0032-1323679. Epub 2012 Sep 12.
Normal circulating PTH in Saudi healthy individuals with hypovitaminosis D.
Al-Saleh Y, Al-Daghri NM, Alkharfy KM, Al-Attas OS, Alokail MS, Al-Othman A, Sabico S, Chrousos GP.
Recent studies in the Middle East have shown an increased incidence of vitamin D deficiency across this region of year-round sunlight. There is scarcity of information, however, as to the levels of 1,25-dihydroxyvitamin D [1,25(OH)2D], the active form of vitamin D, and its associations with cardiometabolic parameters in an Arab cohort and this study aims to fill this gap. In a cross-sectional study, 33 male and 43 female (22 children and 54 adults, total 76) Saudis with previously established low levels of serum 25-hydroxyvitamin D [25(OH)D] (<50 ng/ml or 20 nmol/l) were recruited. Anthropometrics were obtained and fasting blood samples were taken for a routine measurement of glucose, lipid profile, calcium, and albumin, while serum 25(OH)D, 1,25-(OH)2D, and intact PTH were quantified using specific ELISAs. Serum calcium, intact PTH, and 1,25(OH)2D were all within the normal range in both children and adults in both genders. In all subjects, serum 1,25(OH)2D was not associated with intact PTH, while circulating 1,25(OH)D inversely correlated with systolic blood pressure (p=0.01) and waist circumference (p=0.04). Thus, vitamin D deficient Saudi children and adults with normal levels of 1,25-(OH)2D also had normal circulating calcium and PTH. This study suggests that local cutoffs should be set that will be of clinical significance in the identification of those at true risk for harder end-points, such as secondary hyperparathyroidism and bone-related diseases.
© Georg Thieme Verlag KG Stuttgart · New York.
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