Bone mineral density in patients with endogenous subclinical hyperthyroidism: is this thyroid status a risk factor for osteoporosis?

OBJECTIVE: The aim of the present study was to elucidate whether endogenous subclinical hyperthyroidism due to a solitary autonomously functioning thyroid nodule affects bone metabolism and is a risk factor for osteoporosis. DESIGN: In a cross-sectional study measurements of bone mineral density were performed in premenopausal and post-menopausal women. Patients were categorized into non-toxic nodular goitre (n = 32), subclinical hyperthyroid (n = 37) and toxic solitary autonomous thyroid nodule (n = 22) subgroups and the results were compared with those of sex and age-matched control reference population (n = 68). MEASUREMENTS: Lumbar spine and femoral neck bone mineral densities were measured by dual energy X-ray absorptiometry. Single-photon absorptiometry was applied to the measurement of bone mineral content in the midshaft of the radius. RESULTS: In the non-toxic nodular goitre group, bone densities for all the scanned sites did not differ from the sex and age-matched reference population. At the L2-4 scanning site a significant decrease in the bone mineral density could be observed only in the toxic nodular goitre group and this decrease was more marked in the postmenopausal (P < 0.001) than in the premenopausal females (P < 0.05). At the femoral neck and midshaft radius the mean densitometric values were slightly, but significantly, lower only in the post-menopausal subclinical hyperthyroid group compared with the reference population (P < 0.01). The bone mineral density of the femoral neck, as well as the bone mineral content of the midshaft radius, was significantly decreased in both the premenopausal and post-menopausal patients with a toxic solitary nodule. CONCLUSION: This study indicates that the bone mineral density of the lumbar spine, femoral neck and the midshaft of the radius are not significantly decreased in premenopausal patients with endogenous subclinical hyperthyroidism resulting from a solitary autonomously functioning thyroid nodule. Conversely, findings hint at the possibility that long-lasting endogenous subclinical hyperthyroidism may be a contributing factor to the development of osteoporosis in some post-menopausal women, mostly at sites where cortical bone preponderates.

[Mean value of bone mineral content in Hungary measured by dual-photon absorptiometry]. / A csontok ásványianyag-tartalmának magyarországi átlagértékei kettös energiájú rntgenfoton absorptiometriával mért adatok alapján.

Bone mineral content and density of the lumbar spine and femoral neck was measured by dual energy X-ray absorptiometry in normal volunteers (89 women, 77 men) in different age groups. Peak values in both sexes occurred in the 3rd decade and are about 25% higher in men than those in women. In women the bone loss begins around 40 years at lumbar spine and also at the femoral neck. The rate of bone loss in the 6th decade--according to the menopause--significantly accelerates. The diminution in the 8th decade is higher again. In men the decrease of the lumbar spine density is also significant in connection with the ageing process, but the rate of the bone loss is slower, than in women. The femoral neck density and mineral content values begin to decrease at the 4th decade. The decrease of bone mineral content and density of femoral neck are equivalent in both sexes but some difference exists in the velocity. The data were compared with West-european values. The values of the femoral neck are lower, while those of the lumbar spine in the 5th decade in the female are higher in the Hungarian population. The reason of this difference may be the consequence of the obesity of the Hungarian female population.

Relationship between exchangeable body sodium and urinary 6-keto-prostaglandin F1 alpha excretion in normal man.

The renal prostaglandins are involved in the regulation of sodium balance. In the present study exchangeable body sodium (NaE) and the urinary excretion of the stable metabolite of prostacyclin, 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) were determined simultaneously in 10 hospitalized healthy individuals. NaE was 1461 +/- 107 mmol/m2 body surface area, or 98.5 +/- 6.9% when expressed as percent of the normal value assessed on the basis of measurements in 54 control subjects. The excretion of 6-k-PGF1 alpha amounted to 68.3 +/- 39.2 ng/4 hr. Statistical evaluation revealed significant correlation between NaE and PGF1 alpha excretion (r = 0.642; p less than 0.05) and between the serum Na concentration and the urinary excretion of 6-k-PGF1 alpha (r = 0.865; p less than 0.001). The obtained results indicate that urinary 6-k-PGF1 alpha excretion, hence the renal synthesis of prostacyclin, are regulated, among other factors, by body sodium stores. The increased production of prostacyclin with expanding sodium space might be regarded as a compensatory response contributing to the renal elimination of excess sodium from the body. The signal to this response could be the serum Na concentration.

[The role of exchangeable sodium content of the body in cases of hypertension of various etiology]. / A szervezet kicserélhetö nátrium-tartalmának szerepe különbözö aetiológiájú hypertoniákban.

Measurement of exchangeable sodium by isotope dilution is a relatively simple, reliable method for the determination of body sodium contents, which can be used in the clinical practice without significant health hazard to the patient. When computed to body surface area, the values for exchangeable sodium can be compared in patients of different body build. Exchangeable sodium may be variably increased in different clinical conditions associated with hypertension, thus increased sodium contents of the body is of major importance in the pathogenesis of hypertension caused by all forms of mineralocorticoid excess, and in the majority of patients with chronic renal insufficiency. In several endocrine disorders, e. g., acromegaly, hypothyroidism, increased sodium space does not play any significant part in the pathogenesis of hypertension. In diabetes mellitus, exchangeable sodium may be increased already prior to the development of hypertension, however it is still a matter of debate whether this abnormality is involved in the pathogenesis of hypertension in these patients. It seems now beyond any doubt that body sodium is normal in patients with essential hypertension, including those with the low renin form of the disease; nevertheless, some data indicate that blood pressure may be volume dependent in elderly patients with essential hypertension.

Changes with aging in the bone mineral content of the lumbar spine and femoral neck in healthy women in Hungary.

The bone mineral content (BMC) of the lumbar spine and femoral neck was studied in relation to aging in healthy Hungarian women by duel photon-absorptiometric method. The data were compared with North-American and West-European values. The Hungarian values are lower than these for reported from North-America or France, but similar to the BMC values for Sweden. The observed vertebral and femoral bone loss could be well represented by cubic equations. The acceleration of bone loss seems to begin around 40 years. The rate of bone loss was similar to the published values but the decrease in bone loss in the 6th and 7th decades was more suggestive. With regard to the fracture-threshold below which the risk for non-traumatic fractures of vertebrae increases, about 60% of Hungarian women at age 50-59 and about 84% at age 60-69 are considered to be at risk. It is concluded that geographical and habitual differences might be important factors in the development and change of BMC for different populations.

Exchangeable body sodium in normal man: analysis of various frames of reference.

Exchangeable sodium is a reliable measure of body sodium contents. Since fat tissue contains significantly less sodium per unit of weight than other tissues, leanness of an individual may considerably affect exchangeable body sodium. Thus, subjects of different body size can be compared only when body build is considered. To evaluate various frames of reference, we analysed the relationship between exchangeable sodium as determined by isotope dilution and various parameters of body size. Body weight, body height, body surface area, and leanness index correlated significantly with exchangeable sodium, the closest relationship having been obtained with body surface area (r = 0.790; p less than 0.001). When analysing males and females separately (n = 18 and 36, resp.), best parallelism of regression lines was also obtained with body surface area. It is concluded that exchangeable sodium should be referred to unit of body surface area, expressing each individual's value as percent of the normal predicted value calculated from the regression equations y = 1388x + 370 and y = 1554x - 196 for males and females, respectively.

Determination of euthyroid thyroid mass.

Proposals have been made for modification of different formulas used to determine the thyroid weight, by which the 'most probable' value of the normal thyroid mass can be determined. With the help of this method, thyroid masses of euthyroid individuals located in Budapest and its surroundings were determined using a combined scintigraphic and ultrasound method. As an average of 103 cases, the 'most probable' value of normal thyroid mass of the population is 20.9 g (range 15.1-38.8 g).

Effect of 131I therapy on serum calcitonin levels in patients with Graves' disease.

In a group of patients suffering from Graves' disease a transitory fall of serum calcitonin levels and an increase of triiodothyronine concentrations could be detected after 131I therapy. The transient decrease of the calcitonin values might be related to the high radiosensitivity of the parafollicular cells and to a consecutive impairment of calcitonin production, while the rise of triiodothyronine secretion could be explained by the radiation-induced destruction of the thyroid gland. The drop of serum calcitonin levels lasted for a short period only and did not affect serum Ca concentrations, thus the assumption is highly improbable that the temporarily altered calcitonin secretion involves late consequences for the skeletal system after 131I therapy.

Serum calcitonin in hyperthyroidism.

The mineral content of the radius was found to be lower in thyrotoxic than in euthyroid women, particularly in the case of elevated serum triiodothyronine levels. On examining the hormones influencing bone metabolism, the basal serum calcitonin level of thyrotoxic patients was identical with that of the controls. The Ca and calcitonin responses to i.v. Ca loading (3.64 mg CaCl2/kg/3 min) were identical in the euthyroid and hyperthyroid subjects. The results suggest that the calcitonin reserves in Graves' disease are normal and that the bone abnormalities typical of this disease are unrelated to any change in calcitonin secretion. The serum calcitonin levels of patients with subacute thyroiditis were identical with those of the controls. An acute fall in the serum calcitonin level occurred in hyperthyroidism, after radioiodine therapy a finding which might be connected with the high radiosensitivity of the parafollicular cells and with a consecutive impairment of calcitonin production.

Bone mineral content of the healthy aged.

Using Norland-Cameron photon-absorption technique, bone mineral content of 436 healthy aged was measured and compared with that of 198 healthy, aged 21-50. Bone mineral content of postmenopausal females decreased continuously with age and bone mineral content of males began to decrease at age over 70. Bone width and menopausal age seemed to be important factors influencing bone mineral content, but previous physical activity seemed to have no effect on the bone mineral content of the aged.

Effect of the carotid sinus nerve stimulation on nutritive myocardial blood flow in regional cardiac ischaemia.

The authors have studied the local blood flow regulation of the heart under the influence of the stimulation of the carotid sinus nerve in segmental myocardial ischaemia. The experiments were carried out on 38 dogs. By ligating the mid-portion of the left anterior descending coronary artery, a small artificial infarction has been produced. Circulatory examinations were made after 24 hours following the coronary ligation. In 18 dogs the circulatory investigations were done during the electrical stimulation of the carotid sinus nerve while 20 dogs were used as control. The local nutritive blood flow of the heart was measured by the administration of 86 rubidium in the intact zone, in the ischaemia (necrotic) zone and at the border zone of the heart. According to the experimental data, under the influence of the carotid sinus nerve stimulation the blood flow of the intact zone does not change considerably while the necrotic and border zones increases to a great extent. Reflex redistribution of the myocardial blood flow probably plays a decisive role in the antianginal effect of carotid sinus nerve stimulation.