1,721,077 research outputs found
The role of thyroid hormone in blood pressure homeostasis: Evidence from short-term hypothyroidism in humans
No full textArterial hypertension is known to be frequently associated with thyroid dysfunction, with a particularly high prevalence in chronic hypothyroidism. However, to our knowledge no comprehensive study addressed causal mechanisms possibly involved in this association. We here report the physiological relationships between blood pressure and neuro-humoral modifications induced by acute hypothyroidism in normotensive subjects. Twelve normotensive patients with previous total thyroidectomy were studied. Ambulatory 24-h blood pressure monitoring was performed, and free T(3), free T(4), TSH, PRA, aldosterone, cortisol, adrenaline, and noradrenaline were assayed 6 wk after oral L-T(4) withdrawal (phase 1) and 2 months after resumption of treatment (phase 2). During the hypothyroid state (TSH, 68.1 +/- 27.7 muIU/ml; mean +/- SD), daytime arterial systolic levels slightly, but significantly, increased (125.5 +/- 9.7 vs. 120.4 +/- 10.8 mm Hg; P < 0.05), and daytime diastolic levels (84.6 +/- 7.9 vs. 76.4 +/- 6.8 mm Hg; P < 0.001), noradrenaline (2954 +/- 1578 vs. 1574 +/- 962 pmol/liter; P < 0.001), and adrenaline (228.4 +/- 160 vs. 111.3 +/- 46.1 pmol/ liter; P < 0.05) also increased. PRA remained unchanged (0.49 +/- 0.37 vs. 0.35 +/- 0.21 ng/ml.h; P = NS), whereas both aldosterone (310.3 +/- 151 vs. 156.9 +/- 67.5 pmol/liter; P < 0.005) and cortisol. (409.2 +/- 239 vs. 250.9 +/- 113 pmol/liter; P < 0.02) significantly increased. By using univariate logistic regression daytime arterial diastolic values, noradrenaline and aldosterone were found to be significantly related to the hypothyroid state (P < 0.02, P < 0.036, and P < 0.024, respectively). In conclusion, our data show that thyroid hormones participate in the control of systemic arterial blood pressure homeostasis in normotensive subjects. The observed sympathetic and adrenal activation in hypothyroidism, which is reversible with thyroid hormone treatment, may also contribute to the development of arterial hypertension in human hypothyroidism
Is the vascular system a main target for thyroid hormones? From molecular and biochemical findings to clinical perspectives.
No full textPathophysiologic relevance of measuring the plasma levels of cardiac natriuretic peptides in humans
No full textChapter 109 Hypertension and Hypothyroidism: A thyroid dysfunction frequently associated with an abnormal dietary iodine intake
No full textAbstract
Hypertension is a very common disorder. One-third of the United States population have hypertension or are taking anti-hypertensive medications. In addition, 45 million adults in the United States (20% of total population) suffer from pre-hypertension. Hypertension cannot be classified solely by discrete blood pressure thresholds. An important emerging concept is that hypertension is frequently associated with additional co-morbidities that contribute to increasing cardiovascular risk. Actually, hypertension represents a major risk factor for vascular, cardiac, renal and cerebral pathology so that the existence of so- called target organ damage (in vessels, heart, kidney and brain) is a criterion for assessing the clinical severity of the disease. Hypothyroidism represents the most common thyroid function disorder; worldwide, the prevalence of hypothyroidism varies by iodine intake and clearly increases with age, by reaching up to 20% in women older than 60 years. The foremost cause of congenital hypothyroidism remains endemic iodine deficiency and in adults chronic autoimmune (Hashimoto) thyroiditis that is more common in geographic areas of higher dietary iodine. The presence of an association between hypothyroidism and hypertension is an acquisition that has been increasingly confirmed and validated over the time. Results rising from the bulk of the studies suggest a convincing association between hypertension and hypothyroidism, with a prevalence of hypertension in hypothyroid subjects, particularly of elevated diastolic blood pressure nearly triple than that seen in the general population. In subjects over 50 years of age, overall data indicate a 30% prevalence of hypertension in hypothyroid subjects. Moreover, population-based studies revealed the presence of an unrecognized hypothyroidism in 3-5% of untreated hypertensive patients and indicate the existence of a continuous linear relationship between thyroid function and cardiovascular risk regarding what concerns both the atherogenic and metabolic profiles. However, the observed association between hypothyroidism and hypertension does not prove a causal relationship. Considerable further exploration is needed regarding on mechanisms of disease and in particular on the relationships between a hypothyroid state and other (neuro-) endocrine systems that may determine and worsen a hypertensive state. At the same time, new acquisition is necessary to increase our understanding of the role of thyroid hormone deficiency in target organ damage induced by hypertension
Relationship between triiodothyronine and proinflammatory cytokines in chronic heart failure
No full textCytokines and thyroid hormones are involved in the biochemical changes associated to heart failure (HF).
AIM: Aims of the study were to investigate: plasma circulating levels of the cytokines Interleukine-6 (IL-6) TNF alpha and C reactive protein (CRP) in patients with stable HF in relation to the severity of left ventricular dysfunction; the relationship between these inflammatory markers and thyroid hormones.
METHODS: One-hundred and sixty-six patients (121 males, age 64+/-12), with non-ischemic cardiomyopathy, were admitted to the Institute of Clinical Physiology for progressive deterioration of symptoms. Forty-eight healthy subjects (30 males, age range 26-75 years) were also enrolled as control group (Group N). High sensitivity (hs)-IL-6 and hs-TNFalpha were quantified using solid phase sandwich ELISA kits. Hs-CRP was measured by Immulite System.
RESULTS: In the whole population (HF and N), the association between inflammatory markers and age resulted statistically significant only for IL-6 serum concentration (p35% and EF<35%, we clearly observed the progressive enhancement of the inflammatory markers. Considering normal subjects, patients without and with low T3 syndrome, IL-6 and TNFalpha increased progressively from normal to patients with fT3<2 pg/ml (p<0.01 and p<0.01) while CRP only respect to the group with low T3 syndrome (p<0.01). The inflammatory markers were all inversely correlated with FT3 levels.
CONCLUSION: Because low FT3 serum concentration represents a negative prognostic index, it is likely that impairment of T3 production and enhanced inflammation represent pathogenic mechanisms linked to HF progression
Serum thyroglobulin measurement in the follow-up of patients treated for differentiated thyroid cancer.
No full textDetermination of thyroglobulin (Tg) in serum represents a key element in the follow-up of patients treated for differentiated thyroid cancer (DTC). The sensitivity and the specificity of the assay strongly affects the clinical impact. Most of patients are disease-free after thyroidectomy and iodine radioablation; 15% of them show over time persistent or recurrent disease; of these, 5% dies due to worsening of disease. This implies that the follow-up procedures should have a high negative predictive value to reduce as possible the unnecessary diagnostic tools and a high positive predictive value to identify the few patients with persistent/recurrent disease. The recent international guidelines are based on thyroglobulin measurement after thyroid-stimulating hormone (TSH) stimulation. More recent studies suggest that follow up based on serial measurements of basal (i.e. unstimulated) Tg show a higher predictive value than the single measurement after stimulation. Large and multicenter studies are necessary to modify the current guidelines
Thyroid nodule evaluation: what have we really learned from recent clinical guidelines?
No full textRecent guidelines for the evaluation of thyroid nodules clarify the diagnostic algorithm while also reporting important differences. The performance of fine needle aspiration (FNA) for cytological examination follows serum TSH determination and thyroid ultrasonography. Thyroid scintigraphy is recommended following a low TSH value and/or FNA yielding an indeterminate follicular cytology. The use of thyroid ultrasonography is the source of some controversy: though it is recommended as a principal first test, its real-time use to guide FNA ranges from routine to only following an FNA yielding an inadequate or nondiagnostic cytological result. In clinical practice, the proportion of physicians utilizing ultrasonography, scintigraphy and FNA varies and frequently deviates from recommended guidelines. The development of guidelines is necessary to bring about consistency and optimization to the diagnostic work-up of thyroid nodules. It is likely that novel diagnostic procedures, such as molecular markers, large needle aspiration biopsy and thyroid imaging with tracers beyond conventional radioactive iodine or (99m)Tc pertechnetate, will lead to improved performance and implementation of guidelines
- …
