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At least 19 recordsLinked to original sources
PubMed1992

Increased arterial and venous plasma noradrenaline levels in patients with primary hypothyroidism during hypothyroid as compared to euthyroid state.

The use of venous plasma noradrenaline levels as a marker of general sympathetic tone has been questioned as changes in local sympathetic activity may influence the venous levels. To compare arterial and venous plasma noradrenaline levels in patients with primary hypothyroidism, arterial and venous blood were sampled during strictly standardized conditions during hypothyroid and euthyroid states. The patients were hospitalized for 5 days at a metabolic ward on a standardized sodium and potassium intake. On the fourth day catheters were positioned in the axillary artery and vein. Blood samples were drawn simultaneously for noradrenaline and adrenaline determinations during resting conditions. The arterial and venous plasma noradrenaline levels did not differ significantly, neither during hypothyroidism nor during euthyroidism. The arteriovenous difference in plasma adrenaline was similar during hypothyroidism compared to euthyroidism, indicating similar peripheral extraction rate of catecholamines during hypothyroidism as compared to euthyroidism. During hypothyroidism venous and arterial noradrenaline were significantly higher as compared to euthyroidism. In conclusion, there is no difference between arterial and venous noradrenaline levels either in the hypothyroid or the euthyroid state, and the peripheral extraction rate of plasma noradrenaline seems to be similar in hypothyroidism and euthyroidism. The local contribution of noradrenaline from the arm, reflecting local sympathetic nervous activity, is limited during resting conditions. In hypothyroid patients plasma noradrenaline levels are increased as compared to the euthyroid state, indicating increased general sympathetic activity in hypothyroidism.

Adult↗
PubMed1979

Pituitary-thyroid function of fetuses of hypothyroid and growth hormone treated hypothyroid rats.

Maternal hypothyroidism induced by surgical thyroidectomy (Tx) of the rat resulted in significantly higher fetal serum levels of thyroid stimulating hormone (TSH) and thyroxine (T4) on day 22 of gestation. Surprisingly, administration of growth hormone (GH) to hypothyroid mothers increased further the fetal serum T4 and TSH. The in vitro uptake of 131I-T4 by erythrocytes was elevated significantly when incubated with serum from fetuses of both hypothyroid and hypothyroid GH-treated mothers. Although the plasma protein levels of hypothyroid mothers and their fetuses are decreased significantly as compared to controls this is not true of hypothyroid GH-treated mothers and their fetuses. The T4 levels of both groups of Tx mothers were significantly below that of controls. However, as in the case of their fetuses, the serum T4 of GH-treated hypothyroid mothers was elevated from that of Tx only animals. It is concluded that the pituitary-thyroid system of fetuses of hypothyroid mothers is activated excessively during late gestation, that considerable T4 can be transported from the fetus to the mother during this period and that these fetuses are in fact born in a hyperthyroid state which is aggravated by maternal treatment with GH.

Animals↗
PubMed1987

Hypothyroidism and the heart. Examination of left ventricular function in subclinical hypothyroidism.

For revealing whether cardiac performance is changed in subclinical hypothyroidism, the left ventricular ejection fraction (LVEF), a value characterizing left ventricular function, was studied in this clinical state. The results were compared to those obtained in euthyroid subjects and patients with overt hypothyroidism. In a part of subclinical cases, there is a subnormal resting LVEF, which on isometric exercise, increases, but to a lesser extent than in euthyroid controls. In overt hypothyroidism resting LVEF is considerably lower than in euthyroid and subclinically hypothyroid subjects and its value does not respond to exercise. There has been evidence that heterogeneous subclinical hypothyroidism is an intermediate state between euthyroidism and overt hypothyroidism; the majority of patients are euthyroid, a part of them, however, based on systolic time intervals and LVEF studies, are suspect of developing 'tissue' hypothyroidism, although their serum thyroid hormone level is still within normal limits.

Adult↗
PubMed1990

Influence of hypothyroidism and the reversal of hypothyroidism on hemodynamics and cell size in the adult rat heart.

Hypothyroid-induced atrophy of cardiac myocytes was examined in adult female rats in an effort to correlate hemodynamic and cellular changes associated with this disorder. Additional rats were studied 6 weeks after discontinuing antithyroid treatment to determine if structural and functional changes were completely reversible. To induce hypothyroidism, rats were injected daily with propylthiouracil (PTU) for 4 weeks. Control animals were injected similarly with Tris buffer. At the end of the treatment period, hemodynamic measurements were made prior to obtaining isolated myocytes. Cell volume, length, and cross-sectional area were obtained from the septum, and left and right ventricles of treated and untreated rats. After four weeks treatment with PTU, body weight was unchanged but heart weight was significantly reduced by 24%. Characteristic hemodynamic changes associated with hypothyroidism in the rat were noted (eg. reduced heart rate, cardiac output, dP/dtmax, and ventricular pressure). Cell volume was significantly smaller in hypothyroid rats primarily due to a reduction in myocyte cross-sectional area. The hemodynamic and cellular response to hypothyroidism was similar in the right and left ventricle. Six weeks after discontinuing PTU treatment, cellular and hemodynamics changes had returned to normal. It was concluded that hypothyroidism caused a true cardiac atrophy which was reversible. Reduced myocyte cross-sectional area was responsible for most of the myocyte atrophy.

Animals↗
PubMed1978

Difference in pituitary-thyroid feedback regulation in hypothyroid patients, depending on the severity of hypothyroidism.

In an attempt to study pituitary-thyroid interplay during replacement therapy for hypothyroidism, T4 (75-150 micrograms/day) was administered for at least 3 months. A small dose of T4 (75 micrograms/day) significantly depressed basal and TRH-stimulated TSH levels in normal subjects without significantly elevating serum T4 and T3 concentrations. In patients with severe hypothyroidism and marked enlargement of the sella turcica, T4 (2.53 micrograms/kg BW) normalized the serum T4 and slightly elevated the serum T3 but failed to normalize basal and TRH-stimulated TSH levels. In patients with moderate hypothyroidism and moderate enlargement of the sella turcica, T4 (2.0 micrograms/kg BW) normalized serum T4, T3, and basal TSH concentrations but failed to normalize TRH-stimulated TSH levels. In patients with slight hypothyroidism and slight enlargement of the sella turcica, T4 (1.84 micrograms/kg BW) normalized serum T4, T3, and TSH (both basal and TRH stimulated) concentrations. In five patients, an apparent paradoxical increase of basal serum TSH level was found shortly after starting thyroid hormone treatment. It is suggested that pituitary-thyroid interplay during the first 3-6 months of replacement therapy for hypothyroidism varies greatly depending on the severity of hypothyroidism.

Adult↗
PubMed1990

Transient hypothyroidism in infants born to mothers with chronic thyroiditis--a nationwide study of twenty-three cases. The Transient Hypothyroidism Study Group.

To define the difference in prognosis and the clinical features of transient neonatal hypothyroidism in infants born to mothers with chronic thyroiditis, we conducted a nationwide study of this condition. Sixteen mothers with chronic thyroiditis and twenty-three of their offspring with transient hypothyroidism were registered and reported in this paper. Five (group A) of twenty-two live infants showed physical, mental and/or psychomotor developmental delay (IQ below 80). No significant difference between TSH-binding inhibitor immunoglobulin (TBII) or thyroid-stimulation blocking antibody (TSBAb) activities in groups A and B (normal development) were noted. Moreover, there was no significant difference in thyroid function in the newborn period, ages at the start of thyroid medication or the dose and duration of treatment in the two groups. A striking difference observed between the two groups was the thyroid function of their mothers during pregnancy. In group A, four mothers were hypothyroid during pregnancy, and another mother discontinued thyroid medication in the last trimester and her baby was most delayed at the start thyroid medication. On the other hand, the mothers of only two of seventeen live cases in group B had mild hypothyroidism during pregnancy. There were two sets of siblings whose mother received inadequate treatment during the first pregnancy and adequate treatment during the second pregnancy. The psychomotor, physical and mental developmental delay were observed in their first babies. These findings suggested that maternal thyroid function during pregnancy might be an important factor in the prognosis of infants born to mothers with chronic thyroiditis.

Adolescent↗
PubMed1979

Combined hypothalamic hypothyroidism and secondary adrenal insufficiency. Misdiagnosed as primary hypothyroidism.

A case of combined, selective, hypothalamic hypothyroidism and secondary adrenal insufficiency is described. Serum levels of thyroid-stimulating hormone (TSH), before and after thyrotropin-releasing factor (TRF) administration, were in the range generally considered to be indicative of primary, rather than secondary, hypothyroidism. Hence, the clinical usefulness of serum TSH levels to unequivocally provide an accurate distinction between primary and secondary hypothyroidism must be questioned. The paucity of clinical findings suggestive of adrenal insufficiency in this case is emphasized, and the usefulness of adrenal screening tests in hypothyroid subjects seems clear.

Adrenal Insufficiency↗
PubMed1990

Elementary school performance of children with congenital hypothyroidism. New England Congenital Hypothyroidism Collaborative.

The aim of this study was to determine whether hypothyroid children treated early as a result of diagnosis after neonatal screening progressed normally in school. The New England Congenital Hypothyroidism Collaborative studied 72 of its patients at the ages of 9 or 10 years after they had completed 3 years of schooling beyond kindergarten. Control subjects were 96 classmates of the same sex and age as the patients and 32 siblings of appropriate age for the testing. Intelligence quotients (IQs) were measured by the Wechsler Intelligence Scale for Children-Revised abbreviated to five items, and school achievement by the Peabody Individual Achievement Test. In addition, a series of neuropsychologic tests was administered to both patients and control subjects. Educational histories were obtained from the parents for 74 patients, 87 of their siblings, 96 classmates, and 96 siblings of the classmates. The IQ of the control subjects (mean +/- SEM) was 109 +/- 1.2 versus 106 +/- 1.4 for the patients. The mean overall achievement score was 109 +/- 0.93 for the control subjects and 108 +/- 1.3 for the patients. These differences are not statistically significant. The regression lines relating overall Peabody Individual Achievement Test scores or subtests thereof to IQ did not differ among the patients and the control groups. Within the groups the regression lines for IQ and the different subtests of school achievement were also identical. The percentages of children repeating a grade, needing extra tutoring, or in special classes were the same for patients and control groups. We conclude that children with hypothyroidism have no apparent specific impediments to learning unrelated to intelligence.

Child↗
PubMed1992

Subclinical hypothyroidism, overt thyrotoxicosis and subclinical hypothyroidism: the subsequent phases of thyroid function in a patient chronically treated with amiodarone.

In a patient chronically treated with amiodarone, subclinical iodine-induced hypothyroidism occurred as a result of excess iodine released from the amiodarone molecule. The patient was maintained on amiodarone and developed thyrotoxicosis as a result of a destructive process into the thyroid follicles. Amiodarone was withdrawn and methylprednisolone and methimazole treatment was started with resolution of the thyrotoxic phase. Months later, off therapy, the patient developed subclinical hypothyroidism. This is the first description of hypo- and hyperthyroidism in the same patient caused by amiodarone therapy. This unusual observation suggests that patients treated with amiodarone are at risk to develop hyperthyroidism even if they show laboratory findings consistent with hypothyroidism.

Amiodarone↗
PubMed1979

Comparative effectiveness of dextrothyroxine and levothyroxine in correcting hypothyroidism and lowering blood lipid levels in hypothyroid patients.

Data reported here establish that treatment regimens of 4 mg dextrothyroxine and 0.15 mg levothyroxine in hypothyroid subjects produce similar degrees of lowering of serum TSH, cholesterol, triglycerides, and phospholipid levels and equal stimulation of metabolic rate. The Murphy-Pattee total T4 determination applied to blood samples drawn 24 h after the last dose of dextrothyroxine can be used to assess adequacy of treatment. Correction of hypothyroidism requires high serum levels of dextrothyroxine than of levothyroxine. Serum T3 levels increase in patients treated with dextrothyroxine. In the treatment of hypothyroidism, the cholesterol-lowering and metabolic rate-stimulating effects of dextrothyroxine do not appear to be dissociated. Further studies are needed to determine whether such an effect can be demonstrated in euthyroid hypercholesterolemic subjects with doses established herein as equivalent in terms of the stimulating effect on metabolic rate.

Basal Metabolism↗
PubMed1976

[Analysis of in vivo and in vitro radioisotopic tests for studying hypothyroidism. Statistical study of parameters coming from routine investigations in normal subjects and hypothyroid patients].

This report analyses quantitative data collected during spontaneous examination in normal subjects and in hypothyroid subjects, attempting to determine what figures obtained in this way can provide in the diagnosis of this disease. 125I tests in vitro today play a very important role and suffice der detection provided radio-immunoassay is carried out, whether the latter concerns iodine hormones or the thyreotropic pituitary hormone and provided the diagnosis is not confirmed by one single examination. The 131I kinetic test helps in classification of the hypothyroidism. Naturally, only further tests will permit us to determine certain causes (thyroid scan, Querido's test, TRF test, anionic competition, immunological study, etc.). Chemical estimations of stable iodine (127I) no longer have any place in this routine assessment, except that the total iodine is essential to interpret the kinetics in vivo.

Humans↗
PubMed1988

De novo clinical hypothyroidism in pregnancies complicated by type I diabetes, subclinical hypothyroidism, and proteinuria: a new syndrome.

Fifty-one women with type I diabetes who had normal thyroxine values before becoming pregnant were evaluated. Abnormalities of thyroid tests other than thyroxine were encountered in 26 women, of whom 8 developed a low serum thyroxine level, an elevated thyroid-stimulating hormone level, and a low insulin requirement in the second trimester subsequent to an increase in 24-hour urinary protein excretion to greater than 4 gm/24 hr. Thyroid replacement led to an increase in insulin requirement to levels appropriate for gestational age. It is concluded that the woman with type I diabetes who develops proteinuria greater than 4 gm/24 hr during gestation is at risk for the development of de novo hypothyroidism during pregnancy, evidenced by a low serum thyroxine level, an elevated thyroid-stimulating hormone level, and a drop in insulin requirement.

Adult↗