Recombinant human thyroid-stimulating hormone as an alternative for thyroid hormone withdrawal in thyroid cancer management

Total Chemical Synthesis of Human Thyroid-Stimulating Hormone (hTSH) β-Subunit: Application of Arginine-tagged Acetamidomethyl (AcmR) Protecting Groups

The β-subunit of human thyroid stimulating hormone (hTSH) has been synthesized as a single glycoform bearing a chitobiose disaccharide at the native glycosylation site. Key to the successful completion of this synthesis was the introduction of an arginine-tagged acetamidomethyl group, which served to greatly facilitate handling of a glycopeptide fragment with poor aqueous solubility. This general solution to the challenge of working with intractable peptides is expected to find wide use in protein synthesis.

N-Glycoprofiling Analysis for Carbohydrate Composition and Site-Occupancy Determination in a Poly-Glycosylated Protein: Human Thyrotropin of Different Origins

Human thyrotropin (hTSH) is a glycoprotein with three potential glycosylation sites: two in the α-subunit and one in the β-subunit. These sites are not always occupied and occupancy is frequently neglected in glycoprotein characterization, even though it is related to folding, trafficking, initiation of inflammation and host defense, as well as congenital disorders of glycosylation (CDG). For the first time N-glycoprofiling analysis was applied to the site-occupancy determination of two native pituitary hTSH, in comparison with three recombinant preparations of hTSH, a widely used biopharmaceutical. A single methodology provided the: (i) average N-glycan mass; (ii) mass fraction of each monosaccharide and of sulfate; and (iii) percent carbohydrate. The results indicate that the occupancy (65%–87%) and carbohydrate mass (12%–19%) can be up to 34%–57% higher in recombinant hormones. The average glycan mass is 24% lower in pituitary hTSH and contains ~3-fold fewer moles of galactose (p < 0.005) and sialic acid (p < 0.01). One of the two native preparations, which had the smallest glycan mass together with the lowest occupancy and GalNAc, sulfate, Gal and sialic acid contents, also presented the lowest in vivo bioactivity and circulatory half-life. The methodology described, comparing a recombinant biopharmaceutical to its native equivalent, can be applied to any physiologically or clinical relevant glycoprotein.

Low iodine diet for preparation for radioactive iodine therapy in differentiated thyroid carcinoma in Korea

Preparation for radioactive iodine (RAI) therapy includes an increased serum thyroid stimulating hormone level and a low iodine diet (LID). Because of extremely high iodine intake, some physicians have advocated a more stringent LID for greater than 2 weeks in Korean patients with thyroid cancer prior to RAI therapy; however, it is very difficult to maintain a stringent LID for a longer period of time. According to recent reports in Korea, a nonstringent, simple LID for only 1 week might be enough prior to RAI therapy, if the patients can be educated intensively by specially trained staff. The measurement of simple urinary iodine concentration (UIC; µg/L) may underestimate daily iodine excretion in patients with a urinary volume of more than 1 L/day and can also be affected by dilution status. Simple UIC had a weaker correlation than the iodine/creatinine (I/Cr) ratio. Therefore, the urinary I/Cr ratio can replace 24-hour urine iodine excretion instead of simple UIC, although it may overestimate iodine intake in patients with malnutrition or poor muscle mass. The measurement of serum iodine level might be useful as an adjunct parameter for assessing LID preparation, but its sensitivity and specificity were relatively low compared to the urinary I/Cr ratio.

Enhancement of human thyrotropin synthesis by sodium butyrate addition to serum-free CHO cell culture

The influence of sodium butyrate (NaBu) on the synthesis of recombinant human thyrotropin (r-hTSH) by CHO cells was investigated for the first time. A volumetric productivity of ~10 μg hTSH/mL was repeatedly obtained, with a 3.3-fold increase over a control culture carried out in the absence of NaBu. Since NaBu can induce CHO cell apoptosis and cell growth arrest, the increase in specific productivity was even higher, i.e., ca. 5-fold. Analysis of the N-glycan composition of r-hTSH obtained with the addition of NaBu to the culture medium showed an approximately 12 % increase in the amount of sialic acid, as well as in total carbohydrate, partly due to the increase in the site occupancy from 2.77 to 2.93 glycans per mole of hTSH. The two hormone preparations were characterized by N-glycan structural analysis, which showed that NaBu increased the bi-antennary structures by ca. 13 % while decreasing the tri-antennary structures by approximately the same amount. The in vivo biological activity and pharmacokinetic behavior (clearance) were found to be similar for the two hormone preparations.

Low- or high-dose radioiodine remnant ablation for differentiated thyroid carcinoma: a meta-analysis

CONTEXT

There is uncertainty over the dose of (131)I required for thyroid remnant ablation. Most previous studies have been inadequately powered to establish the best fixed dose of (131)I for effective ablation.

OBJECTIVE

The aim of the study was to assess the effects of low- vs high-dose regimens of radioiodine in thyroid remnant ablation for patients with differentiated thyroid carcinoma.

DATA SOURCES

Sources included the Cochrane Library, MEDLINE, EMBASE, and SCOPUS (all until September 2012).

STUDY SELECTION

Randomized controlled trials that assess the efficacy of low- or high-dose of radioiodine ablation of thyroid remnants were collected.

DATA EXTRACTION

Two authors performed the data extraction independently.

DATA SYNTHESIS

Nine randomized controlled trials involving 2569 patients were included. The 1100-MBq vs the 3700-MBq radioiodine showed no statistically significant difference in successful thyroid remnant ablation (risk ratio [RR], 0.91 [0.79 to 1.04]; P = .15), both the 1100 vs the 1850 MBq (RR, 0.95 [0.83 to 1.10]; P = .52) and the 1850 vs the 3700 MBq (RR, 1.00 [0.85 to 1.17]; P = .98) also showed no significant differences (95% confidence intervals were calculated for each estimate). Also, no significant differences existed in quality-of-life scores on the SF-36 between different (131)I-dose groups both on the day of ablation (RR, 0.15 [-0.65 to 0.96], P = .71; I(2) = 29%, P = .24) and 3 months after ablation (RR, -1.1 [-2.37 to 0.17], P = .09; I(2) = 22%, P = .26). A low dose of 1100 MBq radioiodine showed significant benefits in reducing adverse effects (total RR, 0.65 [0.55 to 0.77], P < .1; I(2) = 31%, P =.14) and shorter hospital isolation (RR, 0.4 [0.32 to 0.50]; P < .05).

CONCLUSIONS

The low dose of 1100 MBq radioiodine activity is sufficient for thyroid remnant ablation as compared to 3700 MBq radioiodine activity with similar quality of life, less common adverse effects, and a shorter hospital stay.