Differences between circulating and tissue thyroglobulin in rats.

The mechanism whereby thyroglobulin (TG) reaches the circulation can involve either the release of newly synthesized TG or the release of colloid-stored TG from the thyroid gland. To distinguish between these possibilities, we have compared the properties of circulating and glandular TG in normal and thyroidectomized thyroid tumor-bearing rats. Circulating TG had the properties of poorly iodinated molecules; it was more susceptible to dissociation into subunits and had a lower density, the latter determined by equilibrium centrifugation in concentrated RbCl. The density of circulating TG was the same as that of glandular TG from propylthiouracil-treated rats, suggesting that circulating TG was nearly or completely devoid of iodine. Circulating TG bound to Concanavalin A-Sepharose and had a normal MCR, indicating that mannose was present and galactose was not in terminal positions, both properties of glandular TG. Since previous studies suggest that these properties cannot arise from differential clearance of TG molecules in the periphery, these data suggest that the TG in the circulation may arise from the direct release of poorly iodinated newly synthesized TG from the thyroid.

Iodine content of serum thyroglobulin in normal individuals and patients with thyroid tumors.

We indirectly estimated the iodine content of serum thyroglobulin (TG) in normal individuals and patients with benign and malignant thyroid tumors. Because insufficient TG is present in the serum to perform chemical determinations, equilibrium density centrifugation was used to determine its density, a measure of TG iodine content. In five patients undergoing thyroidectomy, serum TG was compared to TG extracted from the nodules and TG from the surrounding normal thyroid tissue. The iodine content of the tumor TG was much less than that of normal TG in four of the five patients. In patients with benign and malignant nodules, the iodine content of serum TG was lower than that of normal TG, and it was similar in patients with benign and malignant disease. In normal individuals, serum TG was also poor in iodine, similar to the serum TG from the patients, and in the same position as TG with virtually no iodine. These findings are in accord with our report that serum TG in rats is nearly completely devoid of iodine. TG could enter the circulation either by secretion of newly synthesized TG or release of stored TG from the thyroid. The findings show that serum TG in normal individuals does not result from the release of preexisting TG. More likely, it arises from the secretion of poorly iodinated, newly synthesized molecules. Since the elevated serum TG found in patients with nodules also is poor in iodine, it must come directly from the tumor rather than from destruction of surrounding normal thyroid tissue.

Spontaneous growth hormone (GH) secretion by unstimulated human lymphocytes and the effects of GH-releasing hormone and somatostatin.

We investigated in five normal subjects whether the secretion of GH from lymphocytes would occur spontaneously without mitogens and be regulated by GHRH and somatostatin as in the endocrine system. Peripheral blood mononuclear cells were isolated from heparinized blood by the standard Ficoll-Hypaque gradient centrifugation method, and incubated for up to 7 days with or without GHRH, somatostatin analog (SMS 201-995), cycloheximide, or actinomycin D. GH levels in the lyophilized samples were measured by a highly sensitive enzyme immunoassay. GH concentration in culture medium (5 x 10(5) cells/mL) time dependently increased in all subjects, reaching 0.47 +/- 0.18 ng/L at day 7. A protein synthesis inhibitor (cycloheximide) and RNA synthesis inhibitor (actinomycin D) completely blocked GH secretion from lymphocytes. Immunoreactive GH secreted by unstimulated human lymphocytes was similar to pituitary GH in terms of antigenicity and molecular weight. Physiological concentrations of GHRH (10(-10)-10(-8) mol/L) and SMS 201-995 (10(-8)-10(-6) mol/L) had no effects on the spontaneous secretion of GH from human lymphocytes. These results indicate that GH is spontaneously synthesized de novo and secreted from unstimulated human lymphocytes, and that the regulation of GH in the immune system differs from that in the endocrine system.

Growth hormone (GH) secretion from human lymphocytes is up-regulated by GH, but not affected by insulin-like growth factor-I.

Regulation of GH secretion from phytohemagglutinin (PHA)-stimulated lymphocytes was investigated in six normal subjects. Peripheral blood mononuclear cells were incubated with PHA (10 micrograms/mL) in the presence of various amounts of recombinant human GH (0-100 ng/L) and/or recombinant human insulin-like growth factor-I (0-1000 micrograms/L), and the secreted GH was measured by a highly sensitive enzyme immunoassay. PHA-stimulated lymphocytes secreted immunoreactive GH in all subjects (13.6 +/- 2.4 ng/L). Exogenous GH up-regulated the GH secretion in a dose-dependent manner, while IGF-I did not affect either basal GH secretion or the up-regulation by exogenous GH. These findings suggest a difference in the regulation of GH secretion between endocrine and immune systems.

Autoantibody to human prolactin in patients with idiopathic hyperprolactinemia.

We have demonstrated the presence of anti-PRL autoantibody in 5 patients with idiopathic hyperprolactinemia. The clinical features were suggestive of a weak biological activity of PRL, such as regular menses and no galactorrhea. Total PRL levels were markedly elevated (685 +/- 386 micrograms/L) (mean +/- SD) and the proportion of the bound form was 90.7 +/- 7.1%. Scatchard analysis revealed a low-affinity, high-capacity antibody: the association constant was 0.73 +/- 0.56 x 10(7) mol-1 and the maximal binding capacity was 2139 +/- 1792 micrograms/L. Gel filtration study showed that a substantial amount of PRL (64.6 +/- 19.5%) was eluted at the position of 150,000-170,000 mol wt PRL (big-big PRL). Immunoprecipitation study using the chain-specific antibodies showed that the anti-PRL autoantibody belonged to kappa-type immunoglobulin G. These results may indicate that there exists autoantibody-related hyperprolactinemia, especially in those with particularly high serum PRL levels, who had previously been diagnosed as "idiopathic" hyperprolactinemia.

Abnormal thyrotropin-binding immunoglobulins in two patients with Graves' disease.

Among 154 patients with Graves' disease, 2 patients with serum TSH-binding immunoglobulins (Igs) of high affinity were detected by the TSH binding inhibitor Ig (TBII) assay. These IgGs bound 60% and 83% of radioactively labeled TSH, respectively, as determined by polyethylene glycol precipitation, higher than the maximal specific binding (33%) in the TBII assay. Such binding was detected even in the absence of TSH receptors. The addition of bovine TSH (bTSH) or human TSH (hTSH) resulted in dose-dependent reduction in polyethylene glycol-precipitable radioactivity, though hTSH was much less effective. Further, TBII IgGs of high titer or myxedema sera with elevated serum TSH levels did not inhibit the reaction. Scatchard analysis using bTSH revealed that the IgG of 1 patient had a dissociation constant of 4.0 X 10(-11) M and maximum specific binding of 1.6 X 10(-14) M/mg IgG. The 7S fraction was found to be a major binding component by gel filtration chromatography, and immunoelectrophoresis and subsequent autoradiography demonstrated the TSH-binding material to IgG with k-chain in both patients. Both of these patients possessed significant human thyroid stimulator activity and shared 6 of 8 loci in HLA studies. These patients are considered to have anti-TSH antibody, causing falsely increased binding of [125I]bTSH in the TBII assay. Such antibodies result in false TBII assay results and thus should be sought routinely in TBII assays.

Detection and properties of TSH-binding inhibitor immunoglobulins in patients with Graves' disease and Hashimoto's thyroiditis.

TSH-binding inhibitor immunoglobulins (TBII) have been detected in patients with Graves' disease and Hashimoto's thyroiditis by using the radioreceptor assay of TSH. In untreated Graves' patients, TBII levels correlated well with thyroidal 99mTc uptake at 30 min and the grade of epithelial hyperplasia of thyroid follicles. There were many Graves' patients whose sera contained high TBII levels but no detectable bioassayable thyroid-stimulating activity (LATS), and in these patients, close correlation was observed between serum levels of TBII and bioassayable LATS-protector activity. TBII were detectable in 2 (10%) of 20 patients with Hashimoto's thyroiditis, both of whom were clinically hypothyroid. The serum or IgG fraction from one of them, however, did not contain any significant LATS, LATS-protector, or human thyroid adenylate cyclase-stimulating activity and caused inhibition of adenylate cyclase stimulation by TSH. In that patient, TBII may be acting to block TSH binding to TSH receptors, thus causing TSH unresponsiveness and hypothyroidism.

A new in vitro assay for human thyroid stimulator using cultured thyroid cells: effect of sodium chloride on adenosine 3',5'-monophosphate increase.

A new sensitive in vitro assay for human thyroid stimulator (HTS) was developed using human thyroid adenoma cells in monolayer culture. After being cultured for 2 days, the cells were incubated in 0.3 ml Hank's solution without 0.8% NaCl (medium 1) and with thyroid stimulator (bovine TSH or 3 mg patient serum immunoglobulin G) at 37 C for 2 h. The cAMP generated in the cells and the medium during the incubation was measured by RIA. The assay was sensitive enough to elicit a 1.7- to 7.9-fold increase in cAMP at a TSH concentration of 10 microU/ml. HTS was detected in 33 (82.5%) of the 40 patients with untreated graves' disease using this assay system. In Hank's solution (medium 2), however, HTS was detected in only 5 (23.8%) of the 21 patients with untreated GRaves' disease. cAMP increment upon stimulation by either TSH or HTS in medium 1 was larger than that in medium 2, and the difference in the response to HTS using the two media was much greater than that in the response to TSH. Therefore, all HTS-immunoglobulin G studies showed higher activity using medium 1 than using medium 2 when expressed as bovine TSH equivalent. Analysis by the Lineweaver-Burk plot of dose-response curves of the effect of TSH and HTS stimulation on cAMP increment showed an increase in the Km upon the addition of NaCl to the medium. A similar inhibitory effect of NaCl (150 mM) was also observed in the assay system of human thyroid adenylate cyclase stimulator using crude plasma membrane fractions. In summary: 1) an assay for HTS measuring cAMP production in cultured thyroid adenoma cells was developed and the assay using low NaCL medium was found to be the most sensitive, and 2) the inhibitory effect of NaCl on the response to HTS was much greater than that on the response to TSH. These data suggest different behaviors of these two stimulators at their receptor sites.

Role of thyrotropin receptor antibodies in the development of hyperthyroidism: follow-up studies on nine patients with Graves' disease.

TSH binding inhibitor immunoglobulin (TBII) and thyroid-stimulating antibody (TSAb) activities were measured serially for 4-32 months in nine patients before and during development of hyperthyroidism due to Graves' disease. Initially, all were euthyroid, seven had thyroid enlargement, one had proptosis, and seven had high serum titers of antithyroid microsomal antibodies. The occurrence of hyperthyroidism was preceded by detection of both TBII and TSAb in four patients and detection of TSAb alone in four patients. One patient had neither TBII nor TSAb when euthyroid. The mean initial TBII and TSAb activities were 10.2 +/- 15.2% (+/- SD) and 2677 +/- 4620%, respectively, when these patients were euthyroid. When they became hyperthyroid, both TBII and TSAb activities increased in all patients. At that time, TBII was detected in all but one (eight of nine subjects; 88.9%), with a mean activity of 58.8 +/- 23.4% (+/- SD), and TSAb was detected in all nine patients, with a mean value of 4508 +/- 4429%. These findings not only indicate the crucial role of TSH receptor antibodies in the development of hyperthyroidism due to Graves' disease, but also suggest that a certain period of subclinical Graves' disease exists before the onset of overt hyperthyroidism in most patients, in the sense that they have TSH receptor antibodies, especially TSAb, in their serum even though they are euthyroid.

Lung scintigraphy with 51Cr-erythrocytes in Goodpasture's syndrome: case report.

A lung scan using 51Cr-labeled erythrocytes in a patient with Goodpasture's syndrome revealed radioactivity in the lung due to massive intrapulmonary hemorrhage.

Regional metabolic abnormality in relation to perfusion and wall motion in patients with myocardial infarction: assessment with emission tomography using an iodinated branched fatty acid analog.

The clinical usefulness of single-photon tomography using both a beta-methyl-branched fatty acid analog, 123I-15-(p-iodophenyl)-3-methyl pentadecanoic acid (BMIPP) and 201TI was assessed in 4 normal subjects and 28 patients with myocardial infarction. A homogeneous distribution of the tracer in the left ventricular myocardium was observed in each normal subject. BMIPP uptake was decreased compared to 201TI (discordant) in 17/28 patients (61%) and in 49/196 myocardial segments (25%). Such discordant BMIPP uptake was observed more often in areas of acute myocardial infarction (59% at less than or equal to 4 wk versus 31% at greater than 4 wk after onset) (p less than 0.01) and areas supplied with revascularized arteries (74% for revascularized versus 28% for nonrevascularized areas) (p less than 0.01). In addition, the discordant BMIPP uptake was seen more often in the segments exhibiting a wall motion score lower than the perfusion score (46%) in comparison to segments showing a similar decrease in both the wall motion and perfusion scores (12%) (p less than 0.01). Thus, BMIPP imaging may play a major role in increasing our understanding of the relationship between perfusion and wall motion, particularly in patients with acute myocardial infarction and those who received revascularization therapy.

A new imaging agent for medullary carcinoma of the thyroid.

Thyroid scintigraphy, using 99mTc(V) dimercaptosuccinic acid, was performed in four patients with pathologically confirmed medullary thyroid carcinoma and elevated serum calcitonin values. Significant uptake of the tracer was found in the clinically palpable cervical tumor masses, metastatic sites, and residual tumor. This finding, probably specific for medullary thyroid carcinoma, could be of great use in the diagnosis and the surgical follow-up.

Correlation of the antibody titers with serum prolactin levels and their clinical course in patients with anti-prolactin autoantibody.

Patients with anti-prolactin (PRL) autoantibody were surveyed among 208 patients with hyperprolactinemia (PRL > or = 30 micrograms/l) and 228 subjects with normal PRL levels, and the relationship of the antibody titers with serum PRL levels and their clinical course were studied. Diagnosis of possessing the anti-PRL autoantibody was based on the polyethylene glycol method, displacement of the binding of [125I]PRL with the serum by unlabeled PRL and the binding of PRL to protein G, the affinity gel for immunoglobulin G. Prolactin was measured by an immunoradiometric assay that we found was not affected by the anti-PRL autoantibody. A significantly high frequency of anti-PRL autoantibody in patients with idiopathic hyperprolactinemia (16%) and a positive correlation between titers of the autoantibody and serum PRL levels (r = 0.74, p < 0.01) may indicate that the anti-PRL autoantibody itself is another cause of hyperprolactinemia, probably owing to the delayed clearance of PRL. Most patients with anti-PRL autoantibody lacked the clinical symptoms of hyperprolactinemia, such as amenorrhea and galactorrhea, and spontaneous pregnancy occurred despite the marked hyperprolactinemic state, indicating that the biological activity of PRL was attenuated by the autoantibody. In addition, PRL levels and the titers of anti-PRL autoantibody were not changed significantly during the observation period of up to 5 years without any medical intervention. These results suggest that the anti-PRL autoantibody itself is one of the causes of hyperprolactinemia and that medical intervention is unnecessary for this type of hyperprolactinemia.

Effects of anti-prolactin autoantibodies on serum prolactin measurements.

The influence of anti-PRL autoantibodies on PRL measurements determined by immunoassays was investigated in 10 patients with anti-PRL autoantibodies. Four different immunoassay systems (two double-antibody radioimmunoassays (RIAs), a single-antibody RIA and an immunoradiometric assay (IRMA)) were examined. Total and free PRL were extracted from sera by precipitating gamma-globulin with polyethylene glycol with and without acidification, respectively. PRL values determined by direct measurement were compared with total PRL values. The proportion of free to total PRL levels determined by each immunoassay in sera with anti-PRL autoantibodies was significantly lower than in control sera. Values obtained by direct measurement of PRL (a routine assay procedure) in control sera were similar to total PRL values, whereas in sera with anti-PRL (a routine assay procedure) in control sera were similar to total PRL values, whereas in sera with anti-PRL autoantibodies the values varied from one immunoassay to the other. In sera with anti-PRL autoantibodies, double-antibody RIA 1, RIA 2 and single-antibody RIA 3 yielded values lower for PRL than for total PRL (52 +/- 15% in RIA 1, 40 +/- 8.8% in RIA 2, 40 +/- 14% in RIA 3), while PRL levels determined by IRMA were not significantly different (112 +/- 14%). Immunoglobulin G purified from serum with anti-PRL autoantibodies dose-dependently decreased the recovery of PRL assayed by the double-antibody technique, while it did not affect that by IRMA. These data suggest that the presence of anti-PRL autoantibodies gives variable results depending on the immunoassays used.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum growth hormone-binding protein, insulin-like growth factor-I, and growth hormone in patients with liver cirrhosis.

We determined serum growth hormone-binding protein (GHBP), insulin-like growth factor-I (IGF-I), and growth hormone (GH) levels in patients with cirrhosis and in age-matched control subjects, and investigated their relationships. Serum GHBP levels in cirrhotic patients (14.6% +/- 3.9%) (means +/- SD) were significantly lower than those in normal subjects (20.4% +/- 4.7%). GHBP levels had positive correlations with cholinesterase (r = .58, P less than .001) and Normotest (r = .66, P less than .001), both of which represent liver function in cirrhotic patients. Basal GH levels in cirrhotic patients (range, 0.35 to 13.0 micrograms/L; median, 3.9 micrograms/L) were significantly higher than those in normal subjects (0.015 to 6.0 micrograms/L; 0.19 microgram/L). GHBP levels in cirrhotic patients correlated positively with IGF-I levels (r = .39, P less than .01), and negatively with GH levels (r = -.33, P less than .01). These results may indicate that the serum GHBP level reflects the number of hepatic GH receptors, and that the high basal GH level observed in cirrhotic patients is, at least in part, attributable to decreased clearance of GH by these receptors.

Is growth hormone associated with diabetic retinopathy?

The role of growth hormone (GH) in the pathogenesis of diabetic retinopathy was evaluated in 150 patients with non-insulin-dependent diabetes mellitus by measuring urinary GH excretion using a highly sensitive enzyme immunoassay. Urinary GH excretion was not significantly different among diabetic patients without retinopathy (mean, 2.4 ng/day; range, < 0.3-20.0 ng/day), with background retinopathy (2.7 ng/day; < 0.3-22.0 ng/day), and with proliferative retinopathy (3.1 ng/day, 0.9-15.6 ng/day). These data suggest that GH does not play a role for the pathogenesis of diabetic retinopathy through the increased physiological secretion.

Measurement of thyroglobulin in the circulation: clinical and technical considerations.

The concentration of thyroglobulin (TG) in the circulation can be measured by a sensitive, specific, convenient radioimmunoassay. TG is found in the circulation of virtually all normal subjects. It is present in elevated concentrations in patients with a wide variety of thyroid diseases including benign and malignant tumors, multinodular goiter, subacute thyroiditis, Graves' disease and others. At the present time, the most important clinical role of TG measurements is in the evaluation of patients who have been treated for thyroid cancer. As greater clinical correlation is obtained, the usefulness of TG determinations will increase. Anti-TG autoantibodies cause false results in the assay and present the major technical problem which needs to be resolved.

Superior vena cava syndrome due to Graves' disease.

We encountered a patient with Graves' disease showing superior vena cava (SVC) syndrome. The patient was a 72-year-old woman with diffuse nontoxic goiter (diagnosed as chronic thyroiditis); she developed Graves' disease during L-T4 administration. Radioiodine-131 therapy failed to give sufficient effect, and the intrathoracic goiter became enlarged in association with increases in thyroid stimulating antibody activities, followed by the development of SVC syndrome. The surgically excised thyroid gland was diffuse without any nodules. Microscopic findings revealed adenomatous hyperplasia. The present case, though extremely rare, seems important for the understanding of the mechanism of onset of SVC syndrome in relation to thyroid gland enlargement.

Insulinoma with normal plasma insulin concentrations and insulin/glucose ratios during hypoglycemic episodes.

A patient with insulinoma had frequent hypoglycemic episodes with normal plasma insulin levels and insulin/glucose ratios. When immunoreactive insulin (IRI) concentrations in this patient were compared among plasma samples with the same C-peptide immunoreactivity (CPR) levels, the concentrations were significantly lower than in control patients with insulinoma and equal to or lower than those of normal subjects. In hepatic venous samples, CPR levels were significantly higher and the IRI/CPR molar ratios were lower than those in a control subject. These results may indicate that normoinsulinemia in this patient could be explained by increased hepatic extraction of insulin.

Hypokalemic paralysis associated with distal renal tubular acidosis.

A 68-year-old man had hydronephrosis due to ureteral stones for two months earlier and then increasing muscle weakness developed. A 30-year-old woman had rapidly progressive quadriparesis. In both cases, severe hypokalemia with metabolic acidosis was observed and the diagnosis of distal renal tubular acidosis was made. The former was considered to be an idiopathic incomplete form and the latter was a secondary complete form associated with Sjögren syndrome. Hypokalemic paralysis may occur as a complication of distal renal tubular acidosis.