0021-972X/78/4702-0405$02.00/0 Journal of Clinical Endocrinology and Metabolism Copyright © 1978 by The Endocrine Society

Vol. 47, No. 2 Printed in U.S.A.

Altered Responsiveness to Thyrotropin in Thyroid Slices of Graves' Disease Preoperatively Treated with Excess Iodide V

TOSHIMASA ONAYA, MAKOTO MIYAKAWA, MASAO MAKIUCHI, AND RIKIO FURIHATA Department of Medicine, Institute of Adaptation Medicine, and the Second Department of Surgery, Shinshu University School of Medicine, Matsumoto 390, Japan ABSTRACT. In a previous paper, we demonstrated that the acute administration of excess iodide inhibits the adenylate cyclase-cAMP system in mouse thyroid lobes. In the present study, we examined whether presurgical therapy with stable iodide reduces the responsiveness to TSH in thyroid tissues from patients with Graves' disease. Eight patients with Graves' disease were presurgically treated with methimazole and stable iodide and six were given methimazole alone. Normal tissues from five patients with thyroid nodules were also tested. We have found that stimulation by TSH (5 and 50 mU/ml) of cAMP formation in thyroid slices from

T

HERE is considerable evidence that the administration of excess iodide promptly ameliorates symptoms of Graves' disease (1-3). Excess iodide has been shown to inhibit thyroid hormone synthesis and release in hyperactive thyroids of man and animals (4-8). Recent studies have demonstrated several lines of evidence that excess iodide depresses the thyroid adenylate cyclase-cAMP system (9-17). We have recently demonstrated that the acute administration of excess iodide in vivo, a situation similar to iodine therapy for Graves' disease, inhibits cAMP formation induced by thyroid stimulators in mouse thyroid lobes (16). It has been reported that cAMP response to TSH in thyroid tissues from Graves' disease is lowered in comparison to normal thyroids (18-21). The present study was undertaken to clarify whether or not this hyporesponsiveness to TSH in the thyroid of Graves' disease in vitro is due to the preoperative treatment with iodide. We have demonstrated that cAMP reReceived August 25, 1977. Address requests for reprints to: Dr. Toshimasa Onaya, Associate Professor of Medicine, Department of Medicine, Institute of Adaptation Medicine, Shinshu University School of Medicine, Matsumoto 390, Japan.

patients preoperatively treated with methimazole and iodide is significantly less than in slices from patients treated with methimazole alone. Similar observations were also made with other thyroid stimulators, such as prostaglandin E2 and 4-methylhistamine. Furthermore, thyroid slices from patients treated with methimazole alone responded to TSH to the same degree as slices of normal tissues. The data suggest that one of the reasons for the hyporesponsiveness to TSH in thyroids from patients with Graves' disease is preoperative treatment with stable iodide. (J Clin Endocrinol Metab 47: 405, 1978)

sponse to thyroid stimulators is significantly depressed in thyroid tissues from Graves' disease patients preoperatively treated with stable iodide, compared with those treated with methimazole alone. Materials and Methods Thyroid tissues were obtained at surgery from 14 patients with Graves' disease: 8 were treated with

methimazole plus iodide and 6 were treated with methimazole alone preoperatively. Methimazole (30 mg/day) was administered usually for 4-6 weeks, and then stable iodide (20-40 mg/day) was given for 10-14 days before surgery. All patients were euthyroid at the time of operation. The diagnosis of Graves' disease had been made on the usual clinical and laboratory criteria, such as severe symptoms of hyperthyroidism, diffuse goiters, exophthalmos, high values of thyroid hormones in their sera, and high iodine uptake. Normal human thyroid tissues were obtained surgically from five patients with solitary thyroid nodules. In the cAMP study, thyroid slices of 0.5-mm thickness made with a Stadie-Riggs microtome were placed into 10-ml Erlenmeyer flasks containing 2 ml Krebs-Ringer bicarbonate (KRB) buffer (pH 7.4), 50 mg/100 ml glucose, and 1 mM 3-isobutyl-l-methylxanthine (Aldrich Chemical Co.). The flasks were gassed with 95% O2-5% CO2, capped, and incubated at 37 C

405

The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 19:06 For personal use only. No other uses without permission. . All rights reserved.

ONAYA ET AL.

406

for 30 min in a Dubnoff metabolic shaker before addition of the test substances. This preincubation significantly reduced cAMP levels in the control, which subsequently remained constant. After addition of test substances, the flasks were further incubated for 10 min. The incubation was terminated by freezing the slices in test tubes immersed in dry ice-acetone. Before freezing, thyroid slices were lightly blotted on filter paper. Frozen slices were weighed and dropped into boiling cAMP-assay buffer (approximately 10-15 mg wet tissues/0.3 ml 10 mM Tris-HCl, pH 7.5) suspended in a boiling water bath. The tubes were covered to prevent evaporation and boiled for 10 min (22). Thyroid slices were then homogenized with glass homogenizers and denatured protein was removed by centrifugation at 4 C for 20 min. All supernatants were stored at —20 C until the cAMP concentrations were measured. cAMP was measured by the direct binding method of Gilman (23), as described previously (24). The binding protein was obtained by employing the method of Kumon et al. (25). cAMP was purchased from Boehringer-Mannheim Corp., Japan, and bovine TSH (Thytropar) was obtained from Armour. Prostaglandin E2 was kindly supplied by Ono Pharmaceutical Co., and 4-methylhistamine was a generous gift of Dr. R. W. Brimblecombe (Smith, Kline and French Laboratories, Ltd.). Statistical analysis of the significance of difference between groups was done by means of Student's t test. A P value less than 0.05 was considered statistically significant.

JCE&M • 1978 Vol47 • No 2

1.2 10 nR

LLo







S — —

0.4



t

0.2

o IODIDE

(+)

TREATMENT (-) GRAVES'

(-) NORMAL

DISEASE

FIG. 1. cAMP concentrations in thyroid slices (test tissues) from patients with Graves' disease with or without presurgical iodide treatment and patients with thyroid nodules (normal tissues). Thyroid slices were preincubated for 30 min in KRB buffer containing 1 mM 3isobutyl-l-methylxanthine, and then incubated for 10 min

after addition of saline as control. Each point represents a mean of five determinations in the control group in each experiment. Horizontal lines indicate the means of these points in each group, respectively.

1000

700

Results Effects of presurgical iodide treatment on TSH-induced cAMP formation in thyroid slices from patients with Graves' disease The data in Fig. 1 demonstrate that basal cAMP concentrations in control groups after incubation were similar in thyroid slices from patients with Graves' disease with or without iodide treatment and in patients with thyroid nodules (normal tissues). As the basal cAMP concentrations were variable from patient to patient, TSH stimulation of cAMP formation was expressed as a percentage of control in each patient (Fig. 2). In every experiment, two concentrations of TSH (5 and 50 mU/ml) were tested. A low concentration of TSH (5 mU/ml) and a high concentration of TSH (50 mU/ml) caused, respectively, 7- and 18-fold increases in cAMP formation in thyroid slices

TSH (nrU/ml)

0

5

50

FIG. 2. Effects of presurgical iodide treatment on TSHinduced cAMP formation in thyroid slices from patients with Graves' disease. cAMP formation in normal slices from patients with thyroid nodules in response to 50 mU/ml TSH is also shown (A). Thyroid slices were preincubated for 30 min, and then incubated for 10 min after addition of TSH. TSH stimulation was expressed as a percentage of control. Points and vertical brackets indicate mean ± SEM calculated from each mean of five determinations obtained in one experiment for one patient. Parentheses indicate the number of patients.

from patients with Graves' disease presurgically treated with methimazole alone (Fig. 2). In contrast, TSH stimulation of cAMP formation was significantly depressed in thyroid slices from patients treated with methimazole

The Endocrine Society. Downloaded from press.endocrine.org by [${individualUser.displayName}] on 13 November 2015. at 19:06 For personal use only. No other uses without permission. . All rights reserved.

EXCESS IODIDE AND GRAVES' DISEASE

and iodide. For slices from normal tissues, only 50 mU/ml TSH were tested. Normal tissues responded to TSH to the same degree as slices from patients treated with methimazole alone. Effect of iodide treatment on prostaglandin E2 (PGE^-induced cAMP formation in thyroid slices from patients with Graves' disease

v>

>

r

PGE2 is known to be an excellent thyroid stimulator (26-29). In every experiment with thyroid slices of Graves' disease, the effect of PGE2 was also tested (Fig. 3). PGE2, at a concentration of 2.5 X 10"5 M caused a 16-fold increase in cAMP formation in thyroid slices from patients with Graves' disease treated with methimazole alone. In contrast, PGE2 at the same concentration caused only a 6-fold increase in thyroid slices from patients treated with methimazole and iodide. Effect of iodide treatment on 4-methylhistamine-induced cAMP formation in thyroid slices from patients with Graves' disease 4-Methylhistamine, a histamine H2-receptor agonist (30, 31), was also tested. Increases in cAMP formation induced by 4-methylhistamine (10~4 M) in thyroid slices are signifi-

407

cantly different in the two groups of Graves' disease with or without presurgical iodide treatment (Fig. 4). Discussion In addition to the humoral factor hypotheses for the pathogenesis of Graves' disease (32-36), the receptor abnormality hypothesis in the thyroid of Graves' disease has also been put forward (37). Solomon and Chopra (37) raised the possibility that the primary lesion in Graves' disease may be an abnormality in the plasma membrane along the basal surface of the follicular cell, which results in continous activation of adenylate cyclase. Orgiazzi et al. (38), however, have later concluded that hyperthyroidism in Graves' disease is probably not a result of qualitative or quantitative abnormalities in the adenylate cyclase-cAMP protein-kinase system. On the other hand, Kendall-Taylor (18) observed in three patients that thyroid adenylate cyclase activity was less responsive to TSH in Graves' disease than in nontoxic goiter. She did not mention in her report whether these patients had presurgical treatment with stable iodide in addition to antithyroid drugs. Field et al. (19) noted in 10 patients that the TSH response in cAMP accumulation in Graves' disease thyroid tissues preoperatively treated with iodide was less than normal. More recently, Takasu et al. (20, 21) reported that

1300 600 * ~

H300

IS

500

§2

400

P

Altered responsiveness to thyrotropin in thyroid slices of Graves' disease preoperatively treated with excess iodide.

0021-972X/78/4702-0405$02.00/0 Journal of Clinical Endocrinology and Metabolism Copyright © 1978 by The Endocrine Society Vol. 47, No. 2 Printed in U...
531KB Sizes 0 Downloads 0 Views