Hypomagnesemia due to Renal Magnesium Wastage of Unknown Etiology

A twenty-two year old woman, investigated because of tetanic convulsion and refractory hypocalcemia, was shown to have hypomagnesemia, hypokalemia, hypocalciuria and hypophosphaturia. The patient sometimes had loose stool but no steatorrhea. Bowel absorption test of D-Xylose, 131I-triolein and 47Ca were in the normal range. Relative hypermagnesuria was observed despite of hypomagnesemia. Renal function was normal. Parathyroid hormone level was quite low but showed a rapid increase after the injection of magnesium supplement. Normal responsiveness to parathyroid hormone was observed in the kidney. Oral administration of magnesium supplement resulted in relief of subjective symptoms as well as normal serum levels of calcium and potassium. During this period, serum magnesium rose up but never reached the normal level. These findings suggested that renal magnesium wastage of unknown etiology was the significant factor contributing to the hypomagnesemia and that hypocalcemia was probable due to impaired serection of PTH. The mechanism of the hypokalemia observed with the magnesium depletion remains unknown

Risk for Progression to Overt Hypothyroidism in an Elderly Japanese Population with Subclinical Hypothyroidism

Background: Few population-based studies report the changes with time in thyroid function tests in patients with subclinical hypothyroidism. We compared the risk for developing overt hypothyroidism in patients with subclinical hypothyroidism and euthyroid controls from the same population of elderly Japanese. We also sought associations of selected parameters with the development of overt hypothyroidism in the subclinical hypothyroid and euthyroid groups. Methods: We measured thyrotropin (TSH) and free thyroxine (T4) levels at baseline examinations performed from 2000 to 2003 in the cohort of Japanese atomic-bomb survivors and identified 71 patients with spontaneous subclinical hypothyroidism (normal free T4 and TSH >4.5 mIU/L without a history of thyroid treatment, mean age 70 year) and 562 euthyroid controls. We re-examined TSH and free T4 levels an average of 4.2 years later (range, 1.9-6.9). Results: The risk for progression to overt hypothyroidism was significantly increased in subclinical hypothyroid patients (7.0%) compared with control subjects (1.6%) after adjusting for age and sex (odds ratio, 4.56; p=0.009). Higher baseline TSH levels were associated with progression from subclinical to overt hypothyroidism (p=0.02) in the multivariate analysis, including age, sex, antithyroid peroxidase antibody, and ultrasonography (US) findings. The analysis using binary TSH data suggested that a TSH level >8 mIU/L was a predictive value for development of overt hypothyroidism (p=0.005). On the other hand, serum TSH levels spontaneously normalized in 38 (53.5%) of the patients with subclinical hypothyroidism. In the multivariate analysis, normalization of TSH levels was associated with lower baseline TSH levels (p=0.004) and normal and homogenous thyroid US findings (p=0.04). Atomic-bomb radiation dose was not associated with subclinical hypothyroidism or its course. Conclusions: Subclinical hypothyroidism was four times more likely to be associated with development of overt hypothyroidism than euthyroid controls in the sample population of Japanese elderly. TSH levels in half of the patients normalized spontaneously when assessed after an average follow-up period of 4.2 years. Baseline TSH level and thyroid US findings are potential predictors of future thyroid function in subclinical hypothyroidism