Cardiac changes in subclinical and overt hyperthyroid women: retrospective study

BACKGROUND

This retrospective and descriptive 4-year study was undertaken to describe cardiac changes in subclinical and overt hyperthyroidism.

METHODS

We revised the charts of 386 consecutive cardiopathic women whose blood samples were referred to the Radioimmunoassay Laboratory to evaluate thyroid function from 1 January 1997 through 31 December 2000.

RESULTS

After excluding women because euthyroid or hypothyroid, or taking amiodarone and women with hypertension, rheumatic disease, myocardial infarction, a total of 31 hyperthyroid women were thus selected for the study: 19 with subclinical hyperthyroidism and 12 with overt hyperthyroidism. The prevalence of atrial fibrillation did not differ between subclinical (48%) and overt (67%) hyperthyroid women, as well as left atrial dimension; the latter was larger in hyperthyroid (27.8+/-7.8 cm(2)/m(2)) than in control women (18.9+/-2.8 cm(2)/m(2)) (P<0.001). In the subclinical and overt hyperthyroidism, the heart rate (HR) was increased and left ventricular end diastolic (LVED) volume was reduced; in addition, only in overt hyperthyroidism, left ventricular (LV) mass was increased. A significant correlation between LV mass and free triiodothyronine was found.

CONCLUSION

HR increase and LVED decrease, both in subclinical and overt hyperthyroidism, indicate a global impairment of diastolic heart performance, complicated in overt hyperthyroidism by LV concentric hypertrophy. So, in our opinion, subclinical hyperthyroidism, far from being considered a simple laboratory finding, in clinical practice should be taken into serious consideration.

Toxic adenoma and papillary thyroid carcinoma in a patient with Graves' disease

A case of a very rare association of toxic adenoma and papillary carcinoma with Graves' disease is presented. A 34-year-old woman developed Graves' disease with mild ophthalmopathy. An ultrasound revealed diffuse thyroid enlargement with a hypoechoic pattern and a hypoechoic nodule with regular edges of 1.6 cm in diameter at the lower pole of the left lobe. A thyroid 131I scintiscan showed a diffuse and homogeneous 131I distribution. The 131I uptake (RAIU) was elevated. One year later, while still on a low dose of methimazole, the patient had a recurrence of hyperthyroidism following an iodine load from a contrast agent. A further thyroid ultrasound confirmed the previously described pattern but showed a new hypoechoic nodule of 1.1 cm with irregular edges in the left lobe. A thyroid 131I scintiscan this time demonstrated a hyperactive area localised in the larger nodule and a lower diffuse uptake of the remaining tissue. Because of the worsening of the symptoms of hyperthyroidism, the patient had a left lobectomy. On histological examination, the larger nodule was well encapsulated and showed the characteristics of a hyperfunctioning follicular adenoma. The smaller nodule was a typically unencapsulated papillary carcinoma. Several other microfoci of papillary carcinoma were also found in the adjacent tissue. Completion of thyroidectomy was therefore performed, followed by 131I ablative therapy and thyroxine suppressive treatment. This observation suggests that the chronic abnormal stimulation of the thyroid gland by the thyroid-stimulating antibody (TSAb) may facilitate the neoplastic transformation of the thyrocytes in individuals with a critical genetic background.

[Atrial fibrillation and hyperthyroidism. The results of a retrospective study]

BACKGROUND

To examine the prevalence of atrial fibrillation (AF) in cardiopathic patients with hyperthyroidism.

METHODS

The data concerning the patients had been derived from registers of the Laboratory of Radioimmunoassay where cardiopathic patients' blood samples were referred from the Cardiology Unit to evaluate thyroid function, consecutively from January 1992 to December 1997. Of the 443 patients, 303 (68.4%) were classified as being euthyroid, 23 (5.2%) hypothyroid, 117 (26.4%) hyperthyroid. Thyroid function was diagnosed clinically and confirmed by serum TSH and free thyroid hormone (FT3, FT4), levels.

RESULTS

Among hyperthyroid patients, the more frequent arrhythmia was AF (54.7%). After excluding from the study those hyperthyroid patients with rheumatic disease, hypertension, myocardial infarction, 37 hyperthyroid patients were selected; 18 (48.6%), (mean age 63.4 +/- 10.8 yrs), showed sinus rhythm and 19 (51.4%), (mean age 66.0 +/- 12.1 yrs), showed AF. FT3 and FT4 were higher in patients with AF than in those without AF, whereas TSH was not significantly different between the groups. Left ventricular (LV) mass index was significantly increased in hyperthyroid women with AF compared with hyperthyroid women without AF (109.80 +/- 22.33 g/m2 vs 84.50 +/- 6.20 g/m2; p < 0.005). A significant correlation was found between FT3 levels and LV mass index in the hyperthyroid women with and without AF (r = 0.77; p < 0.001).

CONCLUSIONS

In this study the prevalence of AF is 51.4% in hyperthyroid patients. FT3 is higher in patients with AF than in those without AF. Finally, the correlation between FT3 and LV mass index suggests that cardiac hypertrophy is associated with thyroid hyperfunction.

Circulating endothelin-1 levels in type 2 diabetic patients with ischaemic heart disease

To investigate whether circulating endothelin-1 (Et-1) may be related to the increased incidence and severity of ischaemic heart disease in type 2 diabetes mellitus, we compared the concentrations in type 2 diabetic patients and in non-diabetic patients with coronary artery disease (CAD) angiographically documented. Plasma levels of Et-1 were determined in 34 type 2 diabetic patients with CAD (16 with stable angina, 6 with unstable angina, 12 with previous myocardial infarction) and in 19 nondiabetic patients with CAD (4 with stable angina, 5 with unstable angina, 10 with previous myocardial infarction). Fifteen diabetic patients without CAD and 9 healthy volunteers served as control subjects. In the type 2 diabetic patients, the mean Et-1 levels were 3.19 +/- 1.61 pmol/l in those with stable angina, 3.58 +/- 1.92 pmol/l in those with unstable angina, 4.24 +/- 2.53 pmol/l in those with myocardial infarction. These values were not significantly different one another, nor from the values obtained from type 2 diabetic controls (3.64 +/- 2.13 pmol/l). In the non-diabetic patients, the mean Et-1 levels were 3.92 +/- 0.73 pmol/l in those with stable angina, 4.35 +/- 1.67 pmol/l in those with unstable angina, 4.33 +/- 1.66 pmol/l in those with myocardial infarction. These values were not significantly different one another, but significantly higher than those obtained from healthy controls (2.07 +/- 0.67 pmol/l; P < 0.001). No significant differences were found in Et-1 levels between diabetic and non-diabetic patients with stable, unstable angina and previous myocardial infarction. In contrast, a statistically significant difference was found in Et-1 levels between diabetic and non-diabetic control subjects (P < 0.05). In conclusion, similar raised concentrations of Et-1 in diabetic and non-diabetic patients with stable, unstable angina and previous myocardial infarction do not support the hypothesis that higher levels of Et-1 in diabetic patients are responsible for the increased incidence of CAD in diabetes mellitus. However, the raised Et-1 levels found in diabetic patients in the absence of CAD strongly suggest that a generalised endothelial dysfunction, documented in our study by increased levels of Et-1, most probably precedes subsequent cardiovascular diseases.

Plasma endothelin levels in NIDDM patients with macroangiopathy

To determine whether plasma endothelin, a potent vasoconstrictive peptide, is elevated in NIDDM patients, we compared a group of 15 NIDDM patients with macroangiopathy of mean age 60.60 +/- 2.33 years with 15 NIDDM randomly selected matched patients without macroangiopathy. Plasma endothelin levels were significantly increased in NIDDM patients with macroangiopathy (4.22 +/- 0.57 pmol/L) and in NIDDM patients without macroangiopathy (3.81 +/- 0.51 pmol/L). Although endothelin values did not differ between NIDDM groups, both represented significant difference from control values (2.46 +/- 0.24 pmol/L). No significant correlations were found between plasma endothelin and age (rs = 0.11), duration of diabetes mellitus (rs = 0.06), BMI (rs = 0.19), plasma glucose (rs = 0.15), plasma fructosamine (rs = 0.02). These findings confirm that in diabetes mellitus a primary disturbance in endothelin production from vascular endothelium exists as an early phenomenon rather than a result of advanced stage of the disease.

Plasma alanine and lactate concentrations following glucose ingestion in normal and NIDDM subjects

Conflicting evidence has been reported on the metabolic fate of glucose following oral ingestion. We measured the metabolic pattern of gluconeogenic substrates as alanine, predominantly produced by muscle, and lactate after an oral glucose load in ten normal subjects and in eighteen non-insulin dependent diabetes mellitus (NIDDM) subjects. Neither in normal or NIDDM subjects were significant increases in plasma alanine observed, whereas a significant increase in plasma lactate was observed at 60, 90 and 120 min after a glucose load. Although a similar behaviour in plasma alanine and lactate between normal and NIDDM subjects was found, in NIDDM significantly higher levels of plasma alanine and lactate were found at each time. From these observations we conclude: 1) when glucose is ingested under post-absorptive conditions, since plasma alanine levels do not change concurrently with lactate increase, muscle tissue does not play a predominant role in glucose disposal 2) after an oral glucose load, the pattern of gluconeogenic precursors (alanine and lactate) is similar in normal and NIDDM subjects 3) the main cause of fasting and post-prandial hyperglycemia in NIDDM subjects may be due to an overproduction of alanine as well as lactate.

Serum lipoprotein Lp(a) in obesity

Lipoprotein(a) [Lp(a)] has been added to the list of independent risk factors for cardiovascular disease (CVD), whose incidence is greater in obese subjects. There are few data available on the serum Lp(a) concentrations in obese individuals with or without insulin dependent diabetes mellitus (NIDDM). We selected 31 obese men with normal glucose tolerance (NGT) tests, 15 obese diabetic men, 14 non obese diabetic men and 17 healthy men as controls. We measured serum total cholesterol, HDL cholesterol, triglycerides, glucose, insulin and Lp(a). The mean Lp(a) levels in NGT obese men were 70.00 +/- 13.40 mg/l, which were similar to those found in normal controls (75.98 +/- 24.70 mg/l); significantly higher mean Lp(a) levels were found in obese diabetic men (168.84 +/- 56.43 mg/l) and in non obese diabetic men (240.85 +/- 63.35 mg/l). No significant correlation between Lp(a) levels and age, body mass index (BMI), total cholesterol, HDL cholesterol, triglycerides, insulin, was found; only a significant positive correlation between Lp(a) levels and glucose could be revealed (P < 0.05). Since higher levels of Lp(a) were found in NIDDM subjects with or without obesity, we conclude that hyperglycemia may influence the levels of serum Lp(a) facilitating its glycosylation in the liver with the consequence of a decline in its catabolic rate.

Stepwise increase in plasma insulin and C-peptide concentrations in obese, in obese hypertensive, and in obese hypertensive diabetic subjects

Several clinical and epidemiological evidences support the increased risk of cardiovascular disease (CVD) in pathological conditions as obesity, hypertension, non-insulin-dependent diabetes mellitus, which have hyperinsulinemia as a common feature. In this study, we assessed basal plasma insulin (IRI) and C-peptide (CPR) concentrations in 297 volunteers who participated in a survey concerning risk factors of CVD. We found a stepwise increase in fasting insulin and C-peptide levels in normal subjects (IRI 9.10 +/- 0.41 microU/ml; CPR 1.79 +/- 0.08 ng/ml), in obese subjects (IRI 11.31 +/- 0.38 microU/ml; CPR 2.54 +/- 0.07 ng/ml) in obese hypertensive subjects (IRI 14.17 +/- 0.72 microU/ml; CPR 2.64 +/- 0.09 ng/ml), in obese hypertensive diabetic subjects (IRI 22.57 +/- 2.62 microU/ml; CPR 3.33 +/- 0.27 ng/ml). Thus, we found increasing levels of IRI and CPR as normal conditions changed towards progressively more severe pathological conditions. Although several other factors contribute to determine CVD, we conclude that increasing levels of insulin and C-peptide could play an important role in causing CVD.

Erythrocyte glucose, ATP, lactate concentrations and their modifications induced by isologous plasma in non-insulin-dependent diabetes mellitus

We determined erythrocyte glucose, ATP and lactate contents in diabetic subjects using an experimental design in which red blood cells (RBCs) were incubated over four hours in their own plasma and in plasma from normal subjects. The results indicated that baseline RBC glucose and lactate concentrations were higher in diabetic RBCs than in the controls, while ATP content was similar. After incubation, in diabetic RBCs glucose decreased significantly but more markedly when RBCs were incubated in normal plasma; lactate increased markedly in diabetic erythrocytes in their own plasma, but increased to the same extent as controls when incubated in normal plasma. ATP levels were similar to baseline values in diabetic RBCs in their own plasma, but decreased significantly when incubated in normal plasma. Since we found such a different metabolic behaviour in diabetic RBCs changing from diabetic to normal plasma, the important role of blood glucose in regulating RBC glycolysis is again confirmed.

[Plasma levels of beta-endorphin in obese subjects with normal glucose tolerance test and in diabetics]

Forty obese subjects with normal glucose tolerance test (NGTT) thirteen diabetic obese subjects and sixteen normal subjects were studied to evaluate the possible interactions between beta-endorphin (B-Ep) and glucose homeostasis. On the basis of baseline B-Ep levels, two subgroups were selected: one group with normal mean values of B-Ep (7.02 +/- 0.59 pmol/l); another group with elevated mean values of B-Ep (18.95 +/- 1.52 pmol/l). No differences between these subgroups were found as regards body mass index (BMI), insulin and glucagon levels. Normal B-Ep values were found in diabetic obese subjects. No significant correlation was found between B-Ep and BMI, insulin or glucagon. Considering that B-Ep is involved in eating behavior and on the basis of our results, we suggest that elevated B-Ep levels can be found only in those obese NGTT subjects whose obesity is probably related to an abnormal modulation of food intake, such as hyperphagia.

Increase in red cell lactate concentration and its reduction by isologous plasma in NIDDM subjects

We determined red blood cell (RBC) lactate concentrations in NIDDM subjects using an experimental protocol in which diabetic RBCs were incubated over 8 hours both with own plasma and with normal plasma. Furthermore, normal RBCs were incubated both with own plasma and with diabetic plasma. The results indicate that the increased lactate concentrations in RBCs from NIDDM subjects decreased significantly when the same RBCs were incubated in normal plasma. Conversely, lactate concentrations in normal RBCs increased significantly when RBCs were incubated in diabetic plasma. Thus, other than muscle and adipose tissue, RBCs may contribute to increase lactate release for hepatic gluconeogenesis in NIDDM and we suggest that there may be extrinsic plasmatic factor(s) capable of stimulatory effect on diabetic RBC glycolytic pathway.

The effects of muscular exercise on glucose, free fatty acids, alanine and lactate in type I diabetic subjects in relation to metabolic control

Metabolic effects of muscular exercise were studied in eleven subjects with type I diabetes mellitus during poor metabolic control, and again during good metabolic control, and in ten healthy control subjects. All the subjects were submitted to a submaximal gradual triangular test on an electrically braked bicycle ergometer; glucose, FFA, alanine and lactate were measured at rest, and after exercise. In poorly controlled patients, glucose and FFA were unchanged after exercise, whereas blood alanine and lactate increased by a percentage similar to that of the controls, and well-controlled diabetic patients. Baseline alanine concentrations were lower and lactate concentrations higher than in the controls and well-controlled patients. After adequate metabolic control was achieved, in the well-controlled diabetic patients a normalization of pre-exercise alanine and lactate levels and a decrease in blood glucose and FFA after exercise was observed.

Effects of muscular exercise on erythrocyte adenosine triphosphate concentration in patients with insulin-dependent diabetes mellitus

Type I diabetes mellitus represents a metabolic disorder in which intracellular glycolytic pathway is inhibited by insulin deficiency, with the subsequent decreased availability of energetic substrates such as ATP. Some aspects of the energetic metabolism in response to an intensive demand (muscular exercise) were investigated, in a group of 10 ketotic diabetic patients, by measuring erythrocyte adenosine triphosphate (ATP) and blood glucose, free fatty acids (FFA) and lactate levels. In the diabetic subjects, in comparison with normal subjects, the decreased levels of erythrocyte ATP at rest did not increase after exercise, while the increased levels of FFA at rest did not diminish after exercise. The results show that the impaired erythrocyte glycolysis may produce reduced levels of ATP not only at rest, but also after exercise, when muscular contraction results in a manifold increase in cellular energy requirements. In addition, other metabolic systems providing energy for the exercising muscle, such as FFA utilization, are impaired in the ketotic diabetic patients.

Calcium hormones in diabetic pregnancy

To evaluate calcium hormones in diabetic pregnancy, eleven diabetic pregnant women were studied by measuring serum total calcium, phosphorus by conventional methods, and parathyroid hormone, calcitonin and 25-hydroxycholecalciferol, by radioimmunologic methods, serially every four weeks, beginning at 16th week throughout 36th week of gestation. Serum total calcium, phosphorus and parathyroid hormone levels dit not differ between diabetic and non diabetic pregnant women, nor between all pregnant women and age-matched non pregnant healthy women. Serum calcitonin levels, although significantly higher than those of age-matched non pregnant women, did not differ between diabetic and non diabetic pregnant women, maintaining constant with the progression of pregnancy. Serum 25-hydroxycholecalciferol levels, although contained within the normal range, increased significantly in the third trimester of gestation both in non diabetic pregnant women and, even though later, in diabetic pregnant women.

Placental lactogen, progesterone, total estriol and prolactin plasma levels in pregnant women with insulin-dependent diabetes mellitus

Fifteen insulin-dependent diabetic (White's class B-C) and 10 healthy pregnant women were examined from the 12th to the 36th wk. Every 4 wk, a blood sample was drawn to determine total estriol, progesterone, placental lactogen and prolactin. Throughout the pregnancy, total estriol and progesterone in diabetic and non-diabetic women are very similar. On the contrary, the PRL levels are constantly lower in diabetic pregnant women, even though the difference is statistically significant only for the 24th wk determination. The hPL level is instead significantly lower in diabetic pregnant women at the 12th, 20th, 24th, 32nd and 36th wk. A negative correlation exists between the hPL value and the mean blood glucose level, performed the same day as the hormonal test. This correlation is statistically significant at the 12th, 16th, 20th, 28th and 36th wk. No significant difference is found between the two groups examined for the delivery week, the placental weight, the birth weight and the fetal body weight index. To conclude, while estriol and progesterone are not affected by the higher variability of glucose levels during pregnancy in diabetics, compared to normals, hPL and perhaps also PRL may be influenced by the mild hyperglycemia consequent to diabetes.

[Interrelation between gastrin and insulin in a group of normal subjects]

The insulin secretory action of gastrin during O.G.T.T. has been assessed. The insulinaemic and gastrinaemic curves were evaluated in a group of normal subjects submitted to oral glucose load, using radioimmunological measurement techniques. At a later stage, the insulinaemic values were considered in the same subjects after administration of a gastrin analogue (pentagastrin) by the subcutaneous route in a dose such as to provoke a maximal gastric acid response. The data suggest that any participation of gastrin in the regulation of insulin secretion following a glucose meal can be excluded.