Thyroid hormone and parathyroid hormone competing to maintain calcium levels in the presence of vitamin D deficiency.

Weight loss and bone disease in the elderly are very often attributed to malignancy. Rarely, benign treatable conditions may be overlooked. Thyrotoxicosis, a benign treatable condition, needs to be excluded in such patients. The diagnosis may be delayed, since the symptoms are often subtle, and secondary complications including bone disease (osteoporosis) are therefore more frequent at the time of presentation. The case presented here illustrates this well, and also highlights the value of measuring vitamin D levels in such patients. The most interesting aspect of this case was the reciprocal relationship between thyroxine and parathyroid hormone observed in maintaining calcium homeostasis in this thyrotoxic patient with low vitamin D levels.     

Serum calcium,vitamin D and parathyroid hormone relationship among diabetic and non-diabetic pregnant women and their neonates

AimsThe purpose of the study was to determine the prevalence of osteomalacia and hypovitaminosis D among diabetic and non-diabetic pregnant women and in their neonates.MethodsSerum calcium, phosphorus, heat labile alkaline phosphatase, 25(OH) vitamin D and PTH were measured in 32 non-diabetic, 16 gestational diabetic and 8 Type 1 diabetic pregnant women and in cord blood of their newborn.ResultsAmong 32 non-diabetic subjects, 4 subjects (12.5%) had biochemical osteomalacia. 4 out of 16 gestational diabetic subjects (25%) had biochemical osteomalacia whereas 5 out of 8 Type 1 diabetic subjects (62.5%) had biochemical osteomalacia. Mean concentration of 25(OH) vitamin D in the non-diabetic group was 17.18 ± 9.88 ng/ml. Mean concentration of 25(OH) vitamin D in the Gestational diabetic group was 14.75 ± 6.90 ng/ml, while in Type 1 diabetic group, it was 7.81 ± 3.79 ng/ml. 50% of neonates of normal pregnant women had vitamin D deficiency whereas, 50% had vitamin D insufficiency. 40% of neonates of Gestational diabetic pregnant women had vitamin D deficiency whereas, 40% had vitamin D insufficiency.ConclusionVitamin D deficiency and biochemical osteomalacia was present in significant percentage of normal pregnant women and their neonates. Gestational diabetes and Type 1 diabetic women were more prone to develop vitamin D deficiency and biochemical osteomalacia.     

Relationships between vitamin D, parathyroid hormone and bone mineral density in inflammatory bowel disease

Objectives. To explore the relationships between vitamin D intake, serum parathyroid hormone (PTH) and 25-hydroxyvitamin D (250HD) concentrations, and bone mineral density (BMD) in inflammatory bowel disease (IBD).
Setting. A university hospital clinic in Finland.
Subjects. One hundred and fifty randomly selected patients with IBD from the hospital register and 73 healthy controls.
Measurements. BMD of the lumbar spine and the proximal femur was measured with dual energy X-ray absorptiometry. Vitamin D intake and serum levels of 250HD and PTH were determined.
Results. The IBD patients had a lower serum 250HD concentration (28.4 [SD 12.0] nmol L^-1) than the controls (36.1 [16.7] nmol L^-1; P =0.001), whereas no differences in the vitamin D intake or the serum PTH levels were found. The serum 250HD concentrations and the vitamin D intake of the patients with ulcerative colitis ( n =67) were similar to those of the Crohn's disease patients ( n =76). The patients with Crohn's disease of the small bowel had slightly, but not significantly, lower serum 250HD concentrations (25.6 [11.0] nmol L^-1) than the other Crohn's disease patients (31.4 [14.3] nmol L^-1; P =0.061). In the IBD patients, the vitamin D intake and the serum 250HD and PTH concentrations were not associated with BMD.
Conclusions. Patients with IBD have lower serum levels of 250HD than healthy controls, but similar serum PTH concentrations and vitamin D intake. Vitamin D intake, and the serum levels of 250HD and PTH are not associated with BMD, and malabsorption is unlikely to be a major factor in the aetiology of bone loss in unselected IBD patients.     

Prevalence of pathologic vitamin D and parathyroid hormone levels in geriatric patients

Diseases of the bone have always to be considered in geriatric patients, especially because of the therapeutic consequences in osteomalacia (3/100) and hyperparathyreodism (1/100). Therefore calcium, phosphate and alkaline phosphatase should be measured in geriatric patients. The high prevalence of pathologic vitamin D measurements (78/100) in spring points to the importance of outdoor activities.     

The thyroid hormone, parathyroid hormone and vitamin D associated hypertension

Thyroid disorders and primary hyperparathyroidism have been known to be associated with increases in blood pressure. The hypertension related to hypothyroidism is a result of increased peripheral resistance, changes in renal hemodynamics, hormonal changes and obesity. Treatment of hypothyroidism with levo-thyroxine replacement causes a decrease in blood pressure and an overall decline in cardiovascular risk. High blood pressure has also been noted in patients with subclinical hypothyroidism. Hyperthyroidism, on the other hand, is associated with systolic hypertension resulting from an expansion of the circulating blood volume and increase in stroke volume. Increased serum calcium levels associated with a primary increase in parathyroid hormone levels have been also associated with high blood pressure recordings. The mechanism for this is not clear but the theories include an increase in the activity of the renin-angiotensin-aldosterone system and vasoconstriction. Treatment of primary hyperparathyroidism by surgery results in a decline in blood pressure and a decrease in the plasma renin activity. Finally, this review also looks at more recent evidence linking hypovitaminosis D with cardiovascular risk factors, particularly hypertension, and the postulated mechanisms linking the two.     

Intestinal calcium absorption and vitamin D

Vitamin D is required for efficient absorption of dietary Ca. Accumulated observations indicated that active form of vitamin D is involved in the three steps of intestinal Ca absorption:incorporation of Ca by epithelial cells through brush border membrane, intracellular Ca movement, and excretion of Ca into systemic circulation via basolateral membrane. It is also known that activated vitamin D takes part in growth and differentiation of intestinal epithelial cells.     

Effects of a short-term vitamin D(3) and calcium supplementation on blood pressure and parathyroid hormone levels in elderly women

Calcium supplementation is effective in reducing blood pressure in various states of hypertension, including pregnancy-induced hypertension and preeclampsia. In addition, calcitropic hormones are associated with blood pressure. The hypothesis is that short-term therapy with calcium and vitamin D(3) may improve blood pressure as well as secondary hyperparathyroidism more effectively than calcium monotherapy. The effects of 8 weeks of supplementation with vitamin D(3) (cholecalciferol) and calcium on blood pressure and biochemical measures of bone metabolism were studied. The sample consisted of 148 women (mean +/- SD age, 74 +/- 1 yr) with a 25-hydroxycholecalciferol (25OHD(3)) level below 50 nmol/L. They received either 1200 mg calcium plus 800 IU vitamin D(3) or 1200 mg calcium/day. We measured intact PTH, 25OHD(3), 1,25-dihydroxyvitamin D(3), blood pressure, and heart rate before and after treatment. Compared with calcium, supplementation with vitamin D(3) and calcium resulted in an increase in serum 25OHD(3) of 72% (P < 0.01), a decrease in serum PTH of 17% (P = 0.04), a decrease in systolic blood pressure (SBP) of 9.3% (P = 0.02), and a decrease in heart rate of 5.4% (P = 0.02). Sixty subjects (81%) in the vitamin D(3) and calcium group compared with 35 (47%) subjects in the calcium group showed a decrease in SBP of 5 mm Hg or more (P = 0.04). No statistically significant difference was observed in the diastolic blood pressures of the calcium-treated and calcium- plus vitamin D(3)-treated groups (P = 0.10). Pearson coefficients of correlation between the change in PTH and the change in SBP were 0.49 (P < 0.01) for the vitamin D(3) plus calcium group and 0.23 (P < 0.01) for the calcium group. A short-term supplementation with vitamin D(3) and calcium is more effective in reducing SBP than calcium alone. Inadequate vitamin D(3) and calcium intake could play a contributory role in the pathogenesis and progression of hypertension and cardiovascular disease in elderly women.     

The effect of anticonvulsant therapy on serum levels of 25-hydroxy-vitamin D, calcium, and parathyroid hormone.

In 20 female patients treated for 2 to 37 years (mean :12) with anticonvulsant drugs, low serum levels of 25-hydroxy-vitamin D (25-OH-D; 6.4 +/- 3.2 ng/ml M +/- SD), relative hypocalcemia (9.2 +/- 0.4 mg/100 ml) and high levels of parathyroid hormone (PTH 277 +/- 165 pg/ml) were found compared to an age-matched control group (respectively 8.6 +/- 3.2 ng/ml, 9.6 +/- 0.3 mg/100 ml and 183 +/- 95 pg/ml) living in the same psychiatric clinic. A significant negative correlation was found between total duration of treatment and either serum 25-OH-D or serum calcium. After treatment with an oral vitamin D3 supplement (2000 IU/day) for 3 weeks, the serum 25-OH-D levels, although increased, remained lower than normal in the epileptic group and neither hypocalcemia nor their secondary hyperparathyroidism were corrected. These data confirm the occurrence of vitamin D deficiency in patients treated with anticonvulsant drugs resulting in hypocalcemia and secondary hyperparathyroidism.     

Calcium, vitamin D, and parathyroid hormone status in young white and black women: association with racial differences in bone mass

The etiology of the racial disparity in bone mass and fracture rate is unknown. Since the PTH-vitamin D endocrine system is a major regulator of calcium metabolism and bone turnover, this cross-sectional study examined the relationship of radial and lumbar bone density to vitamin D metabolite and PTH concentrations and to calcium intake and excretion in 67 white and 70 black highly comparable, healthy, premenopausal women. Bone density at both radial and lumbar sites was higher in blacks than in whites. Serum 25-hydroxyvitamin D was slightly but not statistically significantly (P = 0.08), lower in blacks than in whites, but there were no racial differences in 1,25-dihydroxyvitamin D, PTH, or renal tubular maximum for reabsorption of phosphate. The mean 25-hydroxyvitamin D concentration in blacks was well within the normal range and was not associated with evidence of secondary hyperparathyroidism. There were no correlations of bone density to vitamin D or PTH concentrations. Although there were no racial differences in dietary intake of calcium and vitamin D or in sodium excretion, 24-h urinary calcium excretion was significantly lower in blacks than in whites, and calcium excretion was inversely associated with radial bone density. In contrast to previous reports, in healthy, normal weight, premenopausal black women there is no evidence of vitamin D deficiency or secondary hyperparathyroidism, suggesting that factors other than the vitamin D-PTH axis are responsible for racial differences in bone mass.