- Crosstalk Between cAMP and Phosphoinositide System in Signal Transduction Pathways Through TSH Receptor.
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Byung Sool Moon, Young Joo Park, Seong Yeon Kim, Bo Youn Cho, Hong Kyu Lee, Do Joon Park
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J Korean Endocr Soc. 2003;18(4):404-413. Published online August 1, 2003
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 Abstract
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- BACKGROUND
TSH stimulates both the adenyl cyclase and phospholipase C (PLC) pathways by binding to a single cell surface receptor that is coupled to G protein, and we examined crosstalk between these two signaling pathways. METHODS: FRTL-5 rat thyroid cells were grown in 6H medium, then incubated with 5H medium before the stimulation. Then cells were incubated for 24 hours with 5H mix containing 1 mCi/L myo-(2-N-3H) inositol. After pretreatment of 100 microM Rp-cAMP, 100 microM forskolin, 50 nM staurosporine, or 100 nM PMA (phorbol-12-myristate-13-acetate), TSH were added in different experiments. After 30 min at 37 degrees C, cells were disrupted and IP formation was determined. RESULTS: Stimulation with 100 microU/mL TSH resulted in a 1.65 fold increase in IP generation. In pursuing the possibility that the two post-receptor events might be linked in some way, we examined the effect of exogenously administrated Rp-cAMP, protein kinase A antagonist, and forskolin, a direct stimulant of protein kinase A, on IP generation achieved at a dose of 100 microU/mL TSH. The pretreatment of 100 M Rp-cAMP at a concentration sufficient to inhibit protein kinase A enhanced TSH-induced IP production. This effect of Rp-cAMP was dose-dependent. Forskolin attenuatedTSH-stimulated increases in phosphatidylinositide turnover. PMA, a protein kinase C (PKC) activator and staurosporine, a PKC inhibitor did not affect TSH-induced IP generation. CONCLUSION: These data suggested that activation of adenylate cyclase/cAMP post-receptor signalling casacde, which results in the protien kinase A activation, has an inhibitory effect on IP turnover activated by TSH.
- Diagnostic Significance of Serum Thyroglobulin Measurement in the Follow - up of Patients with differentiated Thyroid Cancer.
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Seon Hwa Lee, Byung Sool Moon, Sun Wook Kim, Jae Joon Koh, Do Joon Park, Won Bae Kim, Bo Youn Cho, Hong Kyu Lee
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J Korean Endocr Soc. 1999;14(4):667-678. Published online January 1, 2001
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Abstract
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- BACKGROUND
Although serum thyroglobulin (Tg) has been proved to be a good tumor marker in the follow-up of the well differentiated thyroid cancer, some patients show low detectable Tg with negative 131I scan. In the present study, we tried to determine the lowest level of serum Tg which suggests requirement of aggressive work-up for the recurrent or metastatic thyroid cancer. METHODS: Serum Tg levels were measured in 102 patients with well differentiated thyroid cancer who had underwent thyroidectomy followed by 131I ablative therapy. Of 102 patients, 44 patients had no remnant thyroid tissue, while 58 patients had remnant thyroid. Serum Tg levels were measured while TSH-suppressive dose of T4 was administered (on T4 therapy) and then T4 was discontinued for 4 weeks to increase serum TSH level (off T4 therapy), then serum Tg levels were analyzed in relation to the presence or absence of recurrent or metastatic thyroid cancer, assessed by I scan and operation with reference to the physical examination, chest X-ray and thyroid ultrasonogram. RESULTS: Of 102 patients, 16 patients were found to have recurrent or matastatic thyroid cancer. Among them, 10 patients didnt have any remnant thyroid, while 6 patients had remnant thyroid. Serum Tg was undetectable on T4 therapy in 6 patients, but rose higher than 30 ng/mL off T4 therapy in 2 patients, while Tg remained undetectable in other 4 patients. In all 10 patients whoseTg levels were higher than 1 ng/mL. on T4 therapy, Tg rose higher than 30 ng/mL off T4 therapy. The best cut-off value of serum Tg which suggests recurrent or metastatic disease in patients without remnant thyroid was 3 ng/mL on T therapy (sensitivity 60%, specificity 91%, accuracy 84%) and 30 ng/mL off T4 therapy (sensitivity 80%, specificity 75%, accuracy 77%). In patients with remnant thyroid, cut-off value of serum Tg could not be determined because of the low sensitivity and specificity. CONCLUSION: In patients with well differentiated thyroid cancer who have no remnant thyroid, serum Tg level lower than 3 ng/mL on T4 therapy can warrant following-up of patients only with such clinical measures only such as physical examination and thyroid ultrasonogram. However, patients with Tg level of 3 ng/mL or more requires Tg measurements off T4 therapy and 131I scan to evaluate the possibility of recurrent or metastatic thyroid cancer.
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