The pathophysiological role of thyroid blocking antibody (TBAb) in patients with adult primary hypothyroidism and the mechanism of TBAb action were studied. A sensitive bioassay for TBAb, which inhibits the TSH-induced cAMP accumulation, was established using normal human thyroid cells in culture. Thirty-four patients with primary hypothyroidism consisting of 17 goitrous and 17 non-goitrous patients were examined. Two out of 17 goitrous patients (11.8%) and three out of 17 non-goitrous patients (17.6%) were TBAb positive. There were no significant differences between TBAb positive and negative patients in terms of the severity of hypothyroidism or the titers of MCHA or TGHA. Four out of the five TBAb-positive IgGs had strongly positive thyrotropin binding inhibitor immunoglobulin activities. All five TBAb-positive IgGs inhibited the cAMP increase induced by Graves' IgG, but did not affect the action of either prostaglandin E1 or cholera toxin. However, three TBAb positive IgG also inhibited the cAMP increase induced by forskolin. These findings indicate: 1) TBAb is present in hypothyroid patients with autoimmune thyroiditis and TBAb may play a role in the pathophysiology of these patients. 2) TBAb may inhibit the action of TSH not only at the level of the TSH receptor, but also at a different site from the TSH receptor.
HLA antigen phenotypes and BglII restriction fragment length polymorphism of T cell receptor β-chain (TCRβ) gene were analyzed in 61 patients with Graves' disease and 50 patients with Hashimoto's thyroiditis. The antigen frequency of HLA-Bw46 in both Graves' disease (23.0%) and Hashimoto's thyroiditis (24.0%) was significantly higher than that in normal population (8.0%), with relative risks (RR) of 3.45 [corrected P (Pc) < 0.009] and 3.66 (Pc < 0.02), respectively. Significantly increased frequency of HLA-B51 antigen was also found in Hashimoto's thyroiditis (40.0% vs. 16.3% in controls; RR, 3.42; Pc < 0.002). Hybridization of BglII-digested DNA with TCRβ probe revealed two alleles of 9.3 and 8.6 kilobases. The allele frequency of 8.6 kilobases in Graves' disease (79%) and Hashimoto's thyroiditis (76%) was significantly higher (P < 0.01 and P < 0.05, respectively) than that in controls (64%). The frequency of homozygous state 8.6/8.6 was significantly increased in both Graves' disease (62%) and Hashimoto's thyroiditis (60%) over that in controls (39%); the RR of 8.6/8.6 in Graves' disease and Hashimoto's thyroiditis were 2.55 (P < 0.01) and 2.31 (P < 0.05), respectively. These results indicate that in Japanese subjects at least two loci are involved in the susceptibility to Graves' disease and Hashimoto's thyroiditis, one related to HLA and another to TCRβ.
The correlation between T4 5'-deiodinase activity and thyroid hormone concentration in rat tissues was sought. Studies with normal and thyroidectomized rats indicated a significant correlation of the hepatic T3 concentration with the enzyme activity in liver homogenate (r = 0.80, p less than 0.01) or in liver microsomes (r = 0.08, p less than 0.01). The correlation between the hepatic T4 concentration and activity of the enzyme was less significant (r = 0.55, p less than 0.05 for homogenate, and r = 0.66, p less than 0.01 for microsomes). The degree of T4 5'-deiodinase activity in various organs was found to increase in line with tissue concentration of T3. It seems likely that the level of T4 5'-deiodinase activity is controlled by the tissue concentration of T3.
Thyroxine (T4)-binding to serum proteins in primates; catarrhini, prosimiae, and platyrrhini were studied by polyacrylamide gel electrophoresis T4 binding analysis. From the electrophoretic analysis, it was shown that thyroxinebinding proteins similar to human thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) were present in catarrhini and prosimiae species, but not in platyrrhini (callithricidae and cebidae). T4-binding analysis also revealed that catarrhini and prosimiae have a high affinity T4-binding protein similar to human TBG. The association constant (Ka) for T4 of the plasma proteins in these species was approximately 2.0×1010M-1. On the other hand, it was unable to demonstrate a high affinity binding site for T4 in the plasma of platyrrhini species. Both the total and free thyroid hormone concentrations in catarrhini and prosimiae were similar to those in human. Total T4 in cebidae, one of the platyrrhini species, was extremely low. Among 8 animals examined, T4 in 6 was undetectable by radioimmunoassay and the mean T4 of the other two was 2.8μg/dl. However, free thyroid hormone concentrations were similar to those in human. In callithricidae, another platyrrhini species, T4 in plasma was 6.90±2.11, which is comparable to the level in normal human subjects. However, in this species, high-affinity T4-binding protein was lacking and free thyroid hormone concentrations were extremely high (most were higher than the assay limit). Although the thyroid function of callithricidae remains to be studied, it will be interesting if callithricidae is resistant to thyroid hormone action.
The serum bone Gla protein (BGP) level was measured in patients with idiopathic hypoparathyroidism, and primary hyperparathyroidism, and normal volunteers. The mean serum BGP level was 4.5±0.20μg/l in 40 normal volunteers. It was significantly lower in 12 patients with idiopathic hypoparathyroidism (1.6±0.21μg/l, p<0.001) and significantly higher in 33 patients with primary hyperparathyroidism (13.0±1.3μg/1, p<0.001).When a single intravenous injection of 30μg of human PTH 1-34 was administered to the patients with idiopathic hypoparathyroidism, there was no significant change in serum BGP within the next 24 hours. Following a therapeutic oral dose of alfacalcidol, serum BGP was appreciably increased (p<0.001) from the preadministration value of 1.6±0.21μg/l to 3.9±0.34μg/l.In patients with primary hyperparathyroidism, the surgical excision of parathyroid adenoma led to a sharp decrease in serum PTH but a gradual decrease in serum BGP. The latter approximately paralleled the decline in serum alkaline phosphatase.Thus, serum BGP is a marker that reflects bone turnover status in parathyroid disease. It appears that the active form of vitamin D directly increases the secretion of BGP in existing osteoblasts and PTH mainly affects serum BGP to stimulate the bone remodeling cycles with its long term effect.
In order to evaluate the effects of simultaneous administrations of propranolol and glucagon, the changes of plasma human growth hormone (HGH) and other hormones following the oral administration of 40 mg propranolol and the subcutaneous administration of 1 mg glucagon were observed in 9 normal subjects, 8 patients with pituitary dwarfism, 1 with Sheehan's syndrome, 3 with Turner's syndrome, 8 with anorexia nervosa, 1 with Fröhlich's syndrome, 2 with simple obesity, and 1 with hypogonadotropic eunuchoidism. The following results were obtained.(1) In normal subjects, Turner's syndrome, anorexia nervosa, hypogonadotropic eunuchoidism and simple obesity, the peak levels of plasma HGH in P-G administration were more than 8.3 ng/ml, while much lower peak levels were observed in other tests, insulin tolerance test, arginine tolerance test and L-Dopa test. On the other hand, in patients with pituitary dwarfism, Sheehan's syndrome or Fröhlich's syndrome, the peak levels of plasma HGH in P-G administration were less than 4.0 ng/ml.(2) In P-G administration, the significant increase of plasma cortisol level was observed in patients with isolated GH deficiency or anorexia nervosa as well as in normal subjects.(3) The plasma IRG levels increased significantly at 30 to 90 minutes and decreased at 180 minutes after P-G administration, and blood sugar levels increased at 30 to 60 minutes and decreased at 120 to 180 minutes. Plasma FFA revealed the lowest levels at 90 to 120 minutes.(4) Following the, subcutaneous administration of glucagon, plasma IRG increased significantly at 30 minutes, and maintained the high level even at 180 minutes.(5) There was no relationship between changes of plasma HGH level and other hormones.From these data P-G administration seems to be a more potent stimulation test for GH reserve, in comparison with other tests.
It is currently believed that the thyroid stimulating immunoglobulin (TSI) of Graves' disease is involved in the pathogenesis of hyperthyroidism through the stimulation of the adenylate cyclase-cyclic AMP system. To evaluate this mechanism, TSI in the serum of patients with Graves' disease was determined by its ability to generate cyclic AMP (cAMP) in monolayer cells prepared from a normal thyroid gland.The thyroid tissue was digested with collagenase, and the liberated follicles were collected from the supernatant and cultured for 7 days. One gram of thyroid tissue yielded more than 1 × 107 monolayer cells which were stored in aliquots at-80C. Cells (1-2 × 104/0.28 cm2 microtiter well) were incubated for 4 hours in 0.2 ml Hanks solution poor in NaCl, with various amounts of bovine TSH (bTSH) or 1.5 mg/ml Graves' serum IgG extracted by polyethylene glycol. cAMP accumulated in medium and cells was measured by RIA.Total cAMP (both medium and cells) was about 4 times higher when NaCl was deleted from Hanks solution. Moreover, as more than 90% of the cAMP was released into the medium, it was possible to omit the measurement of cellular cAMP, which requires extraction. The increase in medium cAMP concentration was dependent upon the number of cells, incubation time, and dose of bTSH. Time course and dose response curves in medium cAMP stimulated by IgG from 3 Graves' patients paralleled those of bTSH equivalent units. Accordingly, TSI activity could be expressed in bTSH equivalent units (bTSH plUeq). The assay could detect 1.0 or 3.3μU/ml of bTSH and was highly reproducible.TSI activity in all of 16 IgGs from normal subjects was under 3.3 bTSH μUeq/ml, while it was greater than 3.3 bTSHμUeq/ml in IgGs from 33 of 37 (89%) untreated patients with Graves disease. Of the 13 patients followed for 2 to 7 months while on antithyroid drugs, 12 had greater than 3.3 bTSH μUeq/ml and, with the exception of one, all showed a decrease in their TSI activity. Moreover, 5 of 12 patients treated continuously for more than 1 year were TSI negative (<3.3 bTSH μUeq/ml), and except for one case, all had TSI values below 8 bTSH μUeq/ml (a value found in only 25% of untreated patients).This in vitro bioassay for TSI is simple and sensitive. It detects the presence of TSI in virtually 90% of untreated patients with Graves' disease. TSI activity showed a clear decrease during the course of antithyroid drug therapy.
The pituitary-thyroid function and the metabolism of the thyroid hormones in the blood were investigated in 19 patients with Cushings' syndrome before and after an adrenalectomy. 16 patients had adrenal adenomas and 3 patients had modular adrenal hyperplasias.Serum T4, free T4 (FT4), T3, reverse T3 (rT3), TBG and TSH were measured in all patients by radioimmunoassay, and changes in serum TSH, PRL and HGH following the injection of TRH 500 μg in 10 out of 19 patients were observed to evaluate the pituitary functions.Serum T4, FT4 and rT3 were within normal limits and not significantly changed after the surgical treatment. Serum TBG levels in patients before the surgical treatment were also within the normal range. After the treatment, a small but significant increase in TBG levels was observed. Serum TSH levels were suppressed before the surgery and increased after the surgery, but a coefficient of correlation between serum cortisol and TSH levels was not statistically significant.The serum T3 levels were abnormally low in Cushings' syndrome and increased significantly (p<0.001), accompanying the normalization of serum cortisol levels, after the surgical treatment. Moreover, there was a negative correlation between serum T3 and cortisol levels before the treatment (r=-0.586), but it was not statistically significant (before the treatment : T3 0.71 ± 0.04 ng/ml, cortisol 30.2 ± 2.1 μg/dl, after the treatment : T3 1.58 ± 0.15 ng/ml, cortisol 7.5 ± 2.0 μg/dl). To evaluate further the metabolic changes in circulating thyroid hormones, T3/T4, T3/rT3, TBG/T4 and TBG/T3 were compared before and after the adrenalectomy.Significant decreases in T3/T4 (p<0.001) and T3/rT3 (p<0.05) and a significant increase in TBG/T3 (p<0.05) were observed before the surgery. On the other hand, TBG/T4 was not significantly different before or after the surgery.The TSH response to TRH was significantly higher in postoperative patients than in preoperative patients (p<0.05). Before the surgical treatment no responses of serum HGH to TRH were observed in any patients, while after the treatment, abnormal increases from 4.5 ± 1.4 ng/ml to 10 ± 1.1 ng/ml at 15 min. after TRH administration were observed. There was no difference between PRL response to TRH before or after the surgery.These results indicate that the most predominant change in the metabolism of circulating thyroid hormones is the diminution of T3, probably due to the suppression of T4 5′-deiodinase under the circumstances of chronic hypercortisolemia in Cushings' syndrome. Furthermore, it is concluded that in the pituitary gland, not only ACTH is suppressed, but also such other pituitary hormones as TSH, PRL and HGH are modified in various degrees in patients with Cuchings' syndrome.
The serum TPA (tissue polypeptide antigen) concentration was measured to determine whether TPA is usable for differential diagnosis in various surgical endocrine diseases. As for malignant diseases, breast cancer and malignant thyroid diseases were studied as well as benign thyroid diseases and benign adrenal diseases. In some cases, measurement of CEA (cartioembryonic antigen) was also performed for the purpose of comparison. Breast cancer showed a high TPA value and positive ratio of 65% against a positive ratio of 23% by CEA. TPA and CEA values were normal in both malignant and benign thyroid diseases and the positive ratio for each was 0%. In three adrenal diseases, namely pheochromocytoma, Cushing's syndrome and primary aldosteronism, three was a significantly high TPA positive ratio of 97%. All three adrenal diseases simultaneously showed hypertension, renal dysfunction and a diabetes mellitus condition, one of which was presumably cause of the high TPA values. CEA displayed a slightly higher value in pheochromocytoma and a normal value in the other two adrenal diseases. No clear correlation with TPA was observed.
