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Biomedical subjects

M H Jonckheer

Publications and source records attributed to M H Jonckheer.

At least 37 records · Page 2Linked to original sources
PubMed1987

Clinical usefulness of thyroid imaging by means of X-ray fluorescence.

Iodine storage is an important thyroid function which has been difficult to estimate by simple means up to now. The introduction of the X-ray fluorescence technique makes this assessment possible on a large scale, with a minimum radiation burden and no more discomfort for the patient than classical imaging with radioisotopes. Its implementation has resulted in the better understanding of some aspects of thyroid physiopathology. This paper deals with the clinical utility of the method: the visualization of stable iodine and, most important, its quantification contribute significantly, sometimes fundamentally, to a better diagnosis with its therapeutic implications.

Humans↗
PubMed1987

Autoimmune thyroiditis and generalized granuloma annulare: remission of the skin lesions after thyroxine therapy.

A patient suffering from generalized granuloma annulare associated with mild hypothyroidism due to an atrophic autoimmune thyroiditis is presented. Treatment with thyroxine resulted in the restauration of a euthyroid state. Subsequently disappearance of the antithyroid antibodies along with a progressive decrease in the number of the skin lesions was noticed. The association between generalized granuloma annulare and autoimmune thyroiditis has been reported once previously in the literature, but it might be of more frequent occurrence.

Female↗
PubMed1987

Effect of carvedilol on ambulatory blood pressure, renal hemodynamics, and cardiac function in essential hypertension.

A randomized, double-blind, placebo-controlled study was set up to study the effects of acute and chronic administration of carvedilol, a vasodilatory beta-blocker in essential hypertension. Acute administration of a single dose of 50 mg of carvedilol reduced systolic and diastolic blood pressure, without inducing reflex tachycardia. Renal blood flow was preserved; accordingly renal vascular resistance was significantly reduced. A significant reduction of glomerular filtration rate and filtration fraction was observed. Plasma renin activity (PRA) and plasma aldosterone were not changed. Chronic carvedilol treatment produced a significant fall in systolic and diastolic office and ambulatory blood pressure, heart rate, cardiac output, PRA and plasma aldosterone. Blood pressure variability was not changed. Renal blood flow, glomerular filtration rate and filtration fraction also remained unchanged; renal vascular resistance decreased significantly. It is concluded that carvedilol possesses definite antihypertensive and renal vasodilating properties, both acutely and after chronic treatment.

Adrenergic beta-Antagonists↗
PubMed1986

Bone mineral content of the spine with dual photon absorptiometry: normalization of the values.

A Novo Industry BMC-LAB 22a densitometer equipped with a 153Gd source was recently implemented for the measurement of bone mineral content (BMC). 70 females (aged 16 to 86 years) and 67 males (aged 20 to 79 years) were selected to form a reference population. Care was taken to exclude patients with an illness or taking a drug that could influence the measurements, made at the lumbar spine level (L2-L4). Normalization procedures using several parameters (age, length, weight, span, lean body mass, an index of obesity, accepted scans) were developed to try and reduce the large interindividual coefficient of variation (CV). Total BMC values were found to yield a larger CV than when expressed as BMC cm-1. The relation of BMC with age showed a significant linear decrease of 0.3% year-1 for the male population. In the female population the BMC was not correlated with age up to the age of 50 years. Thereafter a linear bone loss of 0.76% year-1 was noted. Correcting for length decreased the CV in males and in females younger than 50 years. The use of the other parameters resulted in no or a very slight improvement. Combining parameters in a multiple regression analysis resulted in a significant decrease of the CV in females older than 50 years only.

Adolescent↗
PubMed1985

Nadolol in essential hypertension: effect on ambulatory blood pressure, renal haemodynamics and cardiac function.

Chronic administration of nadolol has been reported to reduce blood pressure either without or with a concomitant fall of renal blood flow. We therefore studied the effects of nadolol 80 mg once daily on ambulatory blood pressure, renal and systemic haemodynamics in patients with mild to moderate essential hypertension. Ten patients took part in this randomized, double-blind, placebo-controlled, crossover study, each phase of which lasted 4 weeks. Nadolol significantly reduced ambulatory blood pressure and heart rate, but had no effect on blood pressure variability. Cardiac output was significantly reduced by nadolol and total peripheral resistance increased but without reaching statistical significance. Despite the fall in blood pressure and cardiac output, renal blood flow and glomerular filtration rate remained unchanged. The fraction of cardiac output reaching the kidneys rose significantly and renal vascular resistance was significantly reduced. Body weight, urinary sodium excretion and urine flow rate remained unchanged. We conclude that nadolol 80 mg once daily lowers ambulatory blood pressure in patients with mild to moderate hypertension without impairment of renal blood flow, indicating a redistribution of cardiac output to the kidneys. The mechanism of the renal vasodilator effect of nadolol remains to be determined.

Adrenergic beta-Antagonists↗
PubMed1985

Relationship between serum thyroglobulin and intrathyroidal stable iodine in human simple goitre.

Serum thyroglobulin levels are increased in many patients with simple goitre. This increase has been attributed to the release of thyroglobulin (Tg) from the colloid of necrosed follicles. To test the hypothesis that increased serum Tg could be related to the low intrathyroidal iodine concentration [I], the main cause of nontoxic goitre, these two variables were measured in 91 euthyroid goitrous patients and compared to serum free T3 and free T4 levels as well as thyroid weight. Thyroid iodine concentration was estimated from the X-ray fluorescence measurement of intrathyroidal iodine stores and from the weight of the gland estimated by planimetry. Serum Tg levels, the free T3/T4 ratio and thyroid weight were negatively correlated to [I] (Spearman's coefficient of correlation = - 0.44 (P = 0.001); -0.30 (P = 0.006); -0.33 (P = 0.001), respectively). Tg levels were also positively correlated to the T3/T4 ratio (R = 0.28, P = 0.008) and to the weight of the gland (R = 0.37; P = 0.001). These data suggest that, in simple goitre, increased serum Tg concentrations are partly related to the reduced concentration of iodine in goitre tissue (as are an increased T3/T4 ratio and the size of the goitre) and is not only the reflection of follicular necrosis.

Goiter↗
PubMed1985

Thyroid dysfunction in patients on regular hemodialysis: evaluation of the stable intrathyroidal iodine pool, incidence of goiter and free thyroid hormone concentration.

Thyroid function tests and stable intrathyroidal iodine were evaluated in 17 patients on regular hemodialysis treatment (RHD). Triiodothyronine levels in the hypothyroid range, thyroxine levels in the low normal range, but normal levels of thyroid-stimulating hormone, free thyroxine and free triiodothyronine were found. Normal values of stable intrathyroidal iodine and a normal incidence of goiter for our region were also found. It is concluded that in patients on RHD: (1) free thyroid hormone levels are normal and probably represent the most meaningful way of evaluating thyroid function; (2) in our RHD population goiter is no more prevalent than in normal persons; (3) the iodine storage function of the thyroid is not always altered.

Adult↗
PubMed1983

The adaptation of the human thyroid gland to a physiological regimen of iodide intake: evidence for a transitory inhibition of thyroid hormone secretion modulated by the intrathyroidal iodine stores.

The effects of iodide on thyroid function were so far only studied after administration of pharmacological or small continuous doses. We were interested to know how the human thyroid gland would react to a more physiological situation: small doses taken in intermittently. Ten normal male volunteers were given weekly doses of iodide: 1 mg for the first 6 weeks and 2 mg afterwards for another 6 weeks period. Intrathyroidal iodine stores were evaluated by the X-Ray-Fluorescence method. The following thyroid parameters were estimated during the 3 months period: total thyroxine, total triiodothyronine, free thyroxine, free triiodothyronine, reverse triiodothyronine, plasma inorganic iodide, thyroid stimulating hormone and thyrotropin-releasing hormone tests. The following observations were made: i) a steady increase of intrathyroidal iodine (p less than 0.01); ii) no changes in free thyroxine, free triiodothyronine, thyroid stimulating hormone, thyrotropin-releasing hormone test or plasma inorganic iodide. iii) a decrease of total thyroxine (and total triiodothyronine) with a nadir at about 3 weeks and a spontaneous rise afterwards; repetition of this phenomenon by doubling the dose of iodide. It is concluded that 1 mg or 2 mg iodide a week does not inhibit incorporation into the normal human thyroid gland and suggested that these physiological doses of iodide cause a transitory inhibition of thyroxine secretion, representing a form of autoregulation of the thyroid cell, since it was modulated by the intrathyroidal iodine stores and no evidence of pituitary mediation could be evidenced in the experimental protocol.

Adult↗
PubMed1982

Ultrasound examination of the thyroid.

Ultrasound examination of the thyroid offers an accurate morphological picture and the possibility of comparing objectively the size of lobes and lesions over long periods. Cysts and calcifications, mostly benign, are readily recognized. Neoplastic lesions in our series were all less reflective than normal thyroid tissue. But so were the majority of benign nodules. In hyperthyroidism, subacute thyroiditis and Hashimoto's thyroiditis, the thyroid tissue is much less echogenic than in the normal gland.

Adenocarcinoma↗
PubMed1981

Atrophic autoimmune thyroiditis: relationship between the clinical state and intrathyroidal iodine as measured in vivo in man.

The intrathyroidal iodine (ITI) was measured by means of the x-ray fluorescence method in 58 patients suffering from atrophic autoimmune thyroiditis (AAT). They were divided into 4 groups according to their basal T4, basal TSH, and the peak TSH response after TRH administration. Forty-eight normal subjects served as controls. A progressive fall of ITI was found, with less ITI in the first grade AAT patients as compared to the controls. A negative correlation between basal TSH and ITI could be shown. These data support the concept of a graded evolution of AAT, linking the clinical state to the ITI. The results also suggest that, with the hemagglutination techniques used for the determination of antithyroglobulin antibodies and antithyroid microsomal antibodies, positively at a dilution of 1:25 and 1:100, respectively, should be regraded as significant.

Autoimmune Diseases↗
PubMed1981

Amiodarone and the thyroid gland. A review.

The author presents his experience with the thyroid complications of amiodarone therapy: exceptional but sometimes serious conditions. Both, hypo- and hyperthyroidism can occur, probably as a result of the iodine overload on a preexisting thyroid disorder. Amiodarone has an effect on the peripheral conversion of thyroxin which leads to misleading thyroid tests results. Its beta- and alpha-blocking actions affect the clinical features, so that overdiagnosis as well as underdiagnosis are frequent. It is suggested that past or present thyroid disorder, as well as presence of antithyroid antibodies are contraindications for amiodarone therapy.

Amiodarone↗