No evidence for coding region mutations in the retinoblastoma‐associated Kruppel‐associated box protein gene (RBaK) causing familial hyperaldosteronism type II

© 2006 Blackwell Publishing Ltd, Clinical Endocrinology , 65 , 826–831 performed by the same investigator, who was unaware of previous results. Serum TSH was measured on Advia Centaur® analyser (Bayer Diagnostics, Dublin, Ireland). Serum TPOAb and TgAb were measured using commercially available kits (ETI-AB-HTGK and ETI-AB-TPOK, DiaSorin). Reference values were as follows: TSH, 0·35–5·50 mU/l; TPOAb, < 15 KU/l; TgAb, < 100 KU/l. Urinary iodine was measured in 32/56 women using a Urinary Iodine Assay Kit (Bioclone Australia Pty Ltd, Sydney, Australia). In statistical analysis, the paired t -test, the χ 2 -test and Pearson’s analysis were used. P < 0·05 was marked as statistically significant. Body mass index (BMI) in the third trimester of pregnancy was significantly higher than after parturition (mean ± SD, 26·9 ± 4·4 vs 23·7 ± 4·2 kg/m 2 , P < 0·001). Serum TSH and urinary iodine concentrations were within the normal range in the third trimester of pregnancy and after parturition, and were not significantly different ((mean ± SD) 1·522 ± 0·659 vs 1·409 ± 0·741 mU/l, P = 0·41 and (median, range) 198, 68–502 vs 155, 28–485 μ g/g of creatinine, P = 0·2, respectively). As shown in Table 1, mean thyroid volume in the third trimester of pregnancy was 44·5% greater than three to four months after parturition. The mean volume increase (4·4 ± 1·8 ml) in women with previous pregnancies (30/56) did not differ significantly ( P = 0·14) from the value (3·7 ± 1·9 ml) in nulliparous women (26/56). The prevailing CFDS pattern in the third trimester of pregnancy was II, whereas after delivery it was I. Intrathyroid PSV in the third trimester of pregnancy was 56·5% higher than after parturition. A significant correlation between all BMI values and thyroid volumes and between all intrathyroid PSV values and thyroid volumes was found ( r = 0·56, P < 0·0001 and r = 0·41, P = 0·00017, respectively). Our results confirm that thyroid volume and intrathyroidal blood flow decrease after parturition, and therefore must have increased during pregnancy. We have thus provided the first qualitative and quantitative evidence of increased intrathyroidal blood flow during pregnancy. In previous reports, 4 a connection between increased vascularity in the thyroid gland and increased thyroid size was suspected, but never proved. We believe that the present study indirectly proves this hypothesis. Because iodine supply and TSH concentrations did not differ during pregnancy and after parturition, and because PSV correlated well with thyroid volume, it is highly likely that increased intrathyroidal blood flow contributes to thyroid gland enlargement during pregnancy. In conclusion, measurements of intrathyroidal blood flow provide useful additional information on the aetiology of thyroid gland enlargement during pregnancy.