Impairment of GH secretion in adults with primary empty sella

Primary empty sella (PES) is generally not associated with overt endocrine abnormalities, although mild hyperprolactinemia and, in children, deficient GH secretion have been reported. The aim of this multi-center collaborative study was to evaluate basal and stimulated GH secretion in a large series of adult PES patients. The study group consisted of 51 patients [41 women and 10 men, age range: 20-78 yr; (mean+/-SD) 47+/-11 yr]; results were compared with those in normal subjects (Ns) (Ns: no.=110, 55 women, age: 20-50 yr, 37+/-14 yr), and in hypopituitaric patients (HYP) with GH deficiency (HYP: no.=44,17 women, age: 20-72, 49+/-16 yr). Baseline IGF-I levels and GH responses to insulin-induced hypoglycemia (insulin tolerance test, ITT) and/or GHRH+arginine (ARG) stimulation tests were evaluated. PES patients were also subdivided according to BMI in lean (BMI <28 kg/M2 no.=22) or obese (BMI >28 kg/m2 no.=29). PES patients had serum total IGF-I concentrations (mean+/-SE: 142.2+/-9.6 ng/ml) higher than HYP patients (77.4+/-6.4 ng/ml, p<0.001), but lower than Ns (213.3+/-17.2 ng/ml, p<0.005), with no differences between lean and obese PES subjects. The increase in serum GH concentrations following ITT and/or GHRH+ARG stimulation tests, although higher than that observed in HYP patients, was markedly reduced with respect to Ns. No difference was observed in the GH response to provocative tests between lean and obese PES patients. When individual GH responses to ITT or GHRH+ARG were taken into account, a large proportion of PES patients (52% after ITT, 61% after GHRH+ARG) showed a GH peak increase below the 1st centile of normal limits. Serum IGF-I levels in PES patients with blunted GH responses to provocative tests were significantly (p<0.001) lower in PES patients with normal GH responses, and a positive correlation was observed between IGF-I levels and serum GH peak concentrations after GHRH+ARG. In conclusion, the results of the present study provide evidence that adult PES patients often have an impairment of GH secretion, as indicated by the blunted GH response to ITT and GHRH+ARG provocative tests, and by the reduction in serum IGF-I levels. These changes are independent of body mass.

Prevalence of thyroid diseases in patients with acromegaly: results of an Italian multi-center study

Acromegaly is frequently associated with the presence of thyroid disorders, however the exact prevalence is still controversial. An Italian multicenter study was performed on 258 patients with active acromegaly (high levels of IGF-I and lack of suppression of serum GH levels below 2 microg/l after an OGTT). The control group was represented by 150 patients affected by non-functioning and PRL-secreting pituitary adenomas. Two hundred and two out of 258 acromegalic patients (78%) were affected by thyroid disorders with a significantly higher prevalence with respect to the control group (27%, p<0.0001). One hundred and three patients presented (39.9%) non-toxic nodular goiter, 46 (17.8%) non-toxic diffuse goiter, 37 (14.3%) toxic nodular goiter, 1 toxic diffuse goiter (0.4%), 12 (4.6%) Hashimoto's thyroiditis, 3 (1.2%) thyroid cancer. Two patients presented a co-secreting TSH pituitary adenoma. Thirty-six patients had been previously treated for various thyroid abnormalities. Among the 222 acromegalic patients never treated for thyroid disorders thyroid ultrasonography was performed on 194 subjects. Thyroid volume in patients with thyroid abnormalities was 28+/-17.5 ml (median 23) while it was 10.8+/-3.6 ml (median 10) in patients without thyroid disorders (p<0.0001). Thyroid volume was correlated with the estimated duration of acromegaly (r=0.7, p<000.1), but not with age or with serum GH, IGF-I and TSH concentrations. Thyroid volume was higher in acromegalic patients than in the above control population (23.5+/-16.9 ml vs 13.9+/-12.8 ml, p<0.0001). In 62 acromegalic patients 101 fine-needle biopsies of thyroid nodules were performed; 7 nodules were suspicious and the patients were submitted to thyroid surgery: papillary thyroid carcinoma was found in 3 patients. In conclusion, in a large series of acromegalic patients an increased prevalence of thyroid disorders (78%), particularly non-toxic nodular goiter, has been observed. Thyroid volume, evaluated by ultrasonography, was correlated to the estimated duration of acromegaly. Finally, the prevalence of thyroid carcinoma was slightly increased than in the general population.

Primary hyperparathyroidism is associated with an impaired secretion of growth hormone but not of the other anterior pituitary hormones

We have recently reported that GH secretion is impaired in primary hyperparathyroidism (PHP). No systematic assessment of the whole anterior pituitary function in PHP is available. In this study, anterior pituitary function was evaluated in basal and stimulated conditions in a series of 12 consecutive women with PHP. Serum GH secretion was decreased in 9 of 12 PHP patients (75%) confirming our previous results in different series of PHP patients. Instead, at variance, secretion of all the other anterior pituitary hormones was normal. Thus, PHP is associated with an impaired secretion of GH, but not of the other anterior pituitary hormones. The reason why only GH secretion is affected in PHP is unknown.

Iopanoic acid rapidly controls type I amiodarone-induced thyrotoxicosis prior to thyroidectomy

Amiodarone-induced thyrotoxicosis (AIT) may develop either in apparently normal thyroid glands (Type II AIT) or in the presence of sub-clinical thyroid abnormalities (either autonomous goiter or latent Graves' disease; Type I AIT). Mixed forms also occur. While Type I AIT is due to iodine-induced excess thyroid hormone synthesis, Type II AIT is a form of amiodarone (possibly iodine) -induced destructive thyroiditis. Type I AIT is usually treated by combined thionamide and potassium perchlorate therapy, but may be resistant to therapy. On the other hand, Type II AIT often responds favorably to glucocorticoids and may not require further therapy once euthyroidism has been restored. Not infrequently, however, AIT (especially Type I) is resistant to conventional treatment, and several weeks or months may elapse before euthyroidism is restored. Thyroidectomy has been carried out in Type I AIT patients, but thyroid surgery in thyrotoxic patients, especially those with underlying cardiac problems, carries a high surgical risk. In this study we describe 3 patients with Type I AIT, who were successfully treated with a short course of iopanoic acid (IOP), an oral cholecystographic agent, which is rich in iodine and is a potent inhibitor of 5'-deiodinase, resulting in a marked decrease in the peripheral tissue conversion of T4 to T3, in preparation for thyroid surgery. Euthyroidism was rapidly restored in 7-12 days, allowing a subsequent safe and uneventful thyroidectomy in all cases. These patients were then treated with L-T4 for their hypothyroidism and amiodarone was safely re-instituted. We suggest that IOP is the drug of choice in the rapid restoration of euthyroidism prior to definitive thyroidectomy in patients with drug resistant Type I AIT.

Liver transplantation in a case of steatohepatitis and subacute hepatic failure after biliopancreatic diversion for morbid obesity

BACKGROUND

Biliopancreatic diversion (BPD) was designed to avoid the serious complications of jejunoileal bypass (steatohepatitis and hepatic failure). Although this is today considered a safe and effective procedure, a few reports of patients who developed steatohepatitis and subsequently died in hepatic failure exist.

METHODS

We report a morbidity obese patient who developed subacute hepatitis resulting in hepatic failure 1 year after BPD.

RESULTS

Because of irreversible liver failure the decision to perform a liver transplantation was made. The patient underwent emergency liver transplant and lengthening of the common limb. The course of liver transplantation and the patient's recovery were uneventful.

CONCLUSION

Severe liver disease may rarely follow BPD. Liver transplantation and lengthening of the common bowel may be performed to treat these patients.

The Sardinian Autoimmunity Study: 3. Studies on circulating antithyroid antibodies in Sardinian schoolchildren: relationship to goiter prevalence and thyroid function

The relationship among iodine intake, goiter prevalence, and thyroid autoimmunity remains controversial. In the present article, we report the prevalence of antithyroid antibodies (ATA) in relation to iodine intake, frequency of goiter, and thyroid function in a large group of Sardinian schoolchildren living in areas with borderline iodine sufficiency, or mild to moderate iodine deficiency. A total of 8,040 schoolchildren (4,194 males, 3,846 females, ages 6-15 years) from 29 communities were examined between 1986-1994. Thyroid size was assessed by palpation, according to the Pan American Health Organization (PAHO) criteria. In all cases antimicrosomal (MAb) or antithyroid peroxidase antibodies (TPOAb) and thyrotropin (TSH) were assayed. Urinary iodine was determined in a subgroup of 820 children. ATA was detected in 235 (2.92%) sera (88 males, 2.12%; 147 females, 3.82%; chi2 = 20.41, p < 0.0001). ATA prevalence ranged between 0.0%-7.3% in the 29 communities without any geographical correlation with goiter prevalence and urinary iodine excretion. However, ATA was more frequently detected in goitrous children, especially in females. The presence of ATA was not age-dependent in males, whereas a significant increase of ATA was observed in females older than 11 years of age. Seventy-seven (0.96%) children showed borderline to slightly increased serum TSH (>5.2-32 mU/L). Increased serum TSH concentration was more frequently found in children with ATA, especially at higher titers. In summary, our study in Sardinian schoolchildren indicates: (1) ATA display geographical heterogeneity, which seems to be unrelated to goiter prevalence and/or to iodine supply; (2) ATA are more frequently detected in females older than 11 years of age, suggesting that puberty has a role in determining the predominance in females of thyroid autoimmunity; (3) although most goitrous children are ATA-negative, the prevalence of ATA is increased in children with enlarged glands; (4) ATA is associated with an increased prevalence of subclinical hypothyroidism.

Desethylamiodarone antagonizes the effect of thyroid hormone at the molecular level

OBJECTIVE

To evaluate the molecular mechanisms of the inhibitory effects of amiodarone and its active metabolite, desethylamiodarone (DEA) on thyroid hormone action.

MATERIALS AND METHODS

The reporter construct ME-TRE-TK-CAT or TSHbeta-TRE-TK-CAT, containing the nucleotide sequence of the thyroid hormone response element (TRE) of either malic enzyme (ME) or TSHbeta genes, thymidine kinase (TK) and chloramphenicol acetyltransferase (CAT) was transiently transfected with RSV-TRbeta into NIH3T3 cells. Gel mobility shift assay (EMSA) was performed using labelled synthetic oligonucleotides containing the ME-TRE and in vitro translated thyroid hormone receptor (TR)beta.

RESULTS

Addition of 1 micromol/l T4 or T3 to the culture medium increased the basal level of ME-TRE-TK-CAT by 4.5- and 12.5-fold respectively. Amiodarone or DEA (1 micromol/l) increased CAT activity by 1.4- and 3.4-fold respectively. Combination of DEA with T4 or T3 increased CAT activity by 9.4- and 18.9-fold respectively. These data suggested that DEA, but not amiodarone, had a synergistic effect with thyroid hormone on ME-TRE, rather than the postulated inhibitory action; we supposed that this was due to overexpression of the transfected TR into the cells. When the amount of RSV-TRbeta was reduced until it was present in a limited amount, allowing competition between thyroid hormone and the drug, addition of 1 micromol/l DEA decreased the T3-dependent expression of the reporter gene by 50%. The inhibitory effect of DEA was partially due to a reduced binding of TR to ME-TRE, as assessed by EMSA. DEA activated the TR-dependent down-regulation by the negative TSH-TRE, although at low level (35% of the down-regulation produced by T3), whereas amiodarone was ineffective. Addition of 1 micromol/l DEA to T3-containing medium reduced the T3-TR-mediated down-regulation of TSH-TRE to 55%.

CONCLUSIONS

Our results demonstrate that DEA, but not amiodarone, exerts a direct, although weak, effect on genes that are regulated by thyroid hormone. High concentrations of DEA antagonize the action of T3 at the molecular level, interacting with TR and reducing its binding to TREs. This effect may contribute to the hypothyroid-like effect observed in peripheral tissues of patients receiving amiodarone treatment.

The various effects of amiodarone on thyroid function

Amiodarone, a benzofuranic-derivative iodine-rich drug used mostly for tachyarrhythmias, often causes changes in the peripheral metabolism of thyroid hormones mainly due to the inhibition of 5'-deiodinase activity: an increase in serum thyroxine and reverse triiodothyronine, and a decrease in serum triiodothyronine concentrations. Overt thyroid dysfunction, either amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH), occurring in 14% to 18% of patients receiving long-term treatment, may develop both in apparently normal thyroid glands and in glands with preexisting abnormalities. AIH is mainly due to the failure to escape from the acute Wolff-Chaikoff effect, and, in patients with thyroid autoimmune phenomena, to concomitant Hashimoto's thyroiditis. AIT is due to excess iodine-induced thyroid hormone synthesis (type I AIT) or to amiodarone-related destructive thyroiditis (type II AIT), although mixed forms often occur. Treatment of AIH consists of levothyroxine replacement therapy while continuing amiodarone therapy; alternatively, amiodarone can be discontinued, if possible, and the natural course toward euthyroidism can be accelerated by a short trial of potassium perchlorate. In type I AIT, the simultaneous administration of thionamides and potassium perchlorate is the treatment of choice, while in type II AIT steroids are the most useful therapeutic option. Mixed forms are best treated with a combination of thionamides, potassium perchlorate, and glucocorticoids. The low thyroidal 131I uptake usually makes radioiodine therapy not feasible, while thyroidectomy is a valid alternative in cases resistant to medical therapy.

The effects of amiodarone on the thyroid

Amiodarone is a benzofuranic-derivative iodine-rich drug widely used for the treatment of tachyarrhythmias and, to a lesser extent, of ischemic heart disease. It often causes changes in thyroid function tests (typically an increase in serum T(4) and rT(3), and a decrease in serum T(3), concentrations), mainly related to the inhibition of 5'-deiodinase activity, resulting in a decrease in the generation of T(3) from T(4) and a decrease in the clearance of rT(3). In 14-18% of amiodarone-treated patients, there is overt thyroid dysfunction, either amiodarone-induced thyrotoxicosis (AIT) or amiodarone-induced hypothyroidism (AIH). Both AIT and AIH may develop either in apparently normal thyroid glands or in glands with preexisting, clinically silent abnormalities. Preexisting Hashimoto's thyroiditis is a definite risk factor for the occurrence of AIH. The pathogenesis of iodine-induced AIH is related to a failure to escape from the acute Wolff-Chaikoff effect due to defects in thyroid hormonogenesis, and, in patients with positive thyroid autoantibody tests, to concomitant Hashimoto's thyroiditis. AIT is primarily related to excess iodine-induced thyroid hormone synthesis in an abnormal thyroid gland (type I AIT) or to amiodarone-related destructive thyroiditis (type II AIT), but mixed forms frequently exist. Treatment of AIH consists of L-T(4) replacement while continuing amiodarone therapy; alternatively, if feasible, amiodarone can be discontinued, especially in the absence of thyroid abnormalities, and the natural course toward euthyroidism can be accelerated by a short course of potassium perchlorate treatment. In type I AIT the main medical treatment consists of the simultaneous administration of thionamides and potassium perchlorate, while in type II AIT, glucocorticoids are the most useful therapeutic option. Mixed forms are best treated with a combination of thionamides, potassium perchlorate, and glucocorticoids. Radioiodine therapy is usually not feasible due to the low thyroidal radioiodine uptake, while thyroidectomy can be performed in cases resistant to medical therapy, with a slightly increased surgical risk.

Thyroid hormone receptors in neonatal, prepubertal, and adult rat testis

Thyroid hormone (TH) is involved in the differentiation and development of rat testis, whereas its role in adult testis function is still undefined. The aim of our work has been to further analyze the presence in the testis of rats of various ages of messenger RNA (mRNA) coding the different TH receptor (TR) subtypes using a sensitive assay, such as reverse transcriptase-polymerase chain reaction (RT-PCR). To rule out the possibility of an "illegitimate transcription," we have analyzed both T3-binding capacity of adult rat testis and the presence in the same organ of TR proteins by immunohistochemistry, using specific antibodies directed against the various TR isoforms. Messenger RNA coding for TR alpha1 and alpha2 isoforms was clearly visible in gels prepared from RT-PCR samples obtained from the testis of rats of all ages, including adults, whereas mRNA for the TR beta1-beta2 was absent. The T3 maximal binding capacity (Cmax) by nuclear extracts of testicular homogenates gradually decreased from birth to adulthood, still remaining significantly detectable in adult testis, and represented approximately 1% of the Cmax observed in the liver. The immunostaining technique revealed an intense nuclear staining along the basement membrane of testicular tubules prepared from rats of all ages and incubated with an antipeptide antibody specific for TR alpha1 (alpha1-403). Staining with an antipeptide antibody specific for TR beta1 (beta-62) was never present. Our data show that mRNAs coding for the functional TR alpha1, and also for the still undefined alpha2, are present in the testis of rats of all ages. T3-binding activity and immunohistochemical studies confirmed that the message is translated into proteins. The transcriptional activity clearly decreased from birth to adulthood, but it still remained significantly present. The presence of a TR alpha1 message indicates that the adult rat testis may be directly responsive to T3 and, therefore, suggests an action of TH on rat testis that is not only developmental, but also metabolic.

Effects of amiodarone administration during pregnancy on neonatal thyroid function and subsequent neurodevelopment

Amiodarone, a benzofuranic derivative, iodine-rich drug, has been used in pregnancy for either maternal or fetal tachyarrhythmias. Amiodarone, its main metabolite (desethylamiodarone) and iodine are transferred, albeit incompletely, through the placenta, resulting in a relevant fetal exposure to the drug and iodine overload. Since the fetus acquires the capacity to escape from the acute Wolff-Chaikoff effect only late in gestation, the iodine overload may cause fetal/neonatal hypothyroidism and goiter. Among the reported 64 pregnancies in which amiodarone was given to the mother, 11 cases (17%) of hypothyroidism in the progeny (10 detected at birth, 1 in utero) were reported, 9 non-goitrous (82%) and 2 (18%) associated with goiter. Hypothyroidism was transient in all cases, and only 5 infants were treated short-term with thyroid hormones. Only 2 newborns had transient hyperthyroxinemia, associated with low serum TSH concentrations in one. Neurodevelopment assessment of the hypothyroid infants, when carried out, showed in some instances mild abnormalities, most often reminiscent of the Non-verbal Learning Disability Syndrome; however, these features were also reported in some amiodarone-exposed euthyroid infants, suggesting that there might be a direct neurotoxic effect of amiodarone during fetal life. Breast-feeding was associated with a substantial ingestion of amiodarone by the infant, but in the few cases followed it did not cause changes in the newborn's thyroid function. In conclusion, amiodarone therapy during pregnancy may cause fetal/neonatal hypothyroidism and, less frequently, goiter. Thus, the use of amiodarone in pregnancy should be limited to maternal/fetal tachyarrhythmias which are resistant to other drugs or life-threatening. If amiodarone is used during gestation, a careful fetal/neonatal evaluation of thyroid function and morphology is warranted. It seems prudent to advise that fetal/neonatal hypothyroidism be treated, as soon as the diagnosis is made, even in utero, to avoid neurodevelopment abnormalities, although the latter may occur independently of hypothyroidism. If breast-feeding is allowed, careful evaluation of the infant's thyroid function and morphology is required because of the continuing exposure of the infant to the drug.

Amiodarone induces cytochrome c release and apoptosis through an iodine-independent mechanism

Amiodarone (AMD) is one of the most effective antiarrhythmic drugs available. However, its use is often limited by side-effects, mainly hypo- or hyperthyroidism. As AMD displays direct toxic effect on different cell types, we investigated the cytotoxic effect of AMD and its main metabolite, desethylamiodarone (DEA), in thyroid (TAD-2) and nonthyroid (HeLa) cell lines. Both AMD and DEA displayed a dose-dependent toxicity in TAD-2 and HeLa cells, although DEA was more effective. Both TAD-2 and HeLa cells underwent apoptosis, as evidenced by plasma membrane phosphatidylserine exposure and DNA fragmentation. Inhibition of protein synthesis with cycloheximide and inhibition of endogenous peroxidase activity with propylthiouracil did not affect this AMD- and DEA-induced apoptosis in TAD-2 cells. Western blot analysis did not display variations in the expression of p53, Bcl-2, Bcl-XL, and Bax proteins during the treatment with AMD and DEA. Generation of reactive oxygen species, investigated by flow cytometry with dichlorofluorescein diacetate, did not show the production of free radicals during drug treatment. Furthermore, Western blot analysis of cytosolic and mitochondrial fractions prepared from AMD-treated cells demonstrated that AMD induces the release of cytochrome c into the cytosol from the mitochondria. These data indicate that AMD induces cytochrome c release from mitochondria, triggering apoptosis through an iodine-independent mechanism, and that this process is not mediated by modulation of p53, Bcl-2, Bcl-XL, or Bax protein expression and does not involve the generation of free radicals.

Changes of serum TSH level during oral glucose tolerance test: comparison of morning and evening test with plain circadian TSH rhythm

OBJECTIVE

To compare the changes of TSH level in serum during oral glucose tolerance test (OGTT) with those resulting from a plain circadian rhythm and, in addition, to compare such changes between the morning and evening hours.

METHODS

Oral glucose tolerance tests were performed in groups of 8-20 adults after the oral administration of glucose (75 g in 400 ml tap water) at 8.00, 10.00 and 20.00 h. Blood samples for the estimation of TSH (supersensitive IRMA method) were taken in 30 min intervals for following 3 hours. In the same groups of subjects the blood samples were obtained between 8.00 and 13.00 h or between 20.00 and 23.00 h one week later for the assessment of plain circadian rhythm of TSH levels.

RESULTS

The level of TSH in a group subjected to OGTT at 8.00 h was significantly decreased (P<0.05) between 8.30 and 10.30 h, i.e. 30-150 min after glucose administration which was parallel to the circadian decrease found in the same subjects. However, this was followed by an increase of TSH up to the original level reached at 11.00 h which was contrasting to a circadian decrease. Similar pattern was found also when OGTT was started at 10.00 h. In a group subjected to the evening OGTT at 20.00 h similar decrease of TSH level was found at 21.00 h which was contrasting to the circadian increase. However, this was followed by a remarkable increase of TSH level between 21.00 and 23.00 h which was parallel to the circadian trend, but much more abrupt than that found without the previous administration of glucose.

CONCLUSIONS

In both the morning and evening OGTT a decrease of TSH level was found between 30 and 90 min after glucose administration which was followed by an increase between 90 and 180 min after that. The decrease during the morning test was parallel to the circadian trend, while the increase was opposite to that. However, an inverse figure was found in the evening test, the decrease of TSH being opposite and following increase being parallel to the circadian trend.

Minimally invasive video-assisted surgery of the thyroid: a preliminary report

BACKGROUND

Endoscopic thyroidectomy has not yet met the favor of most endocrine surgeons. We evaluated the technical feasibility of a video-assisted approach to thyroid surgery.

PATIENTS AND METHODS

The study group comprised 22 females and 5 males, all with a single thyroid nodule. The nodule was "hot" in 4 patients, microfollicular in 17 and with Hürthle cell cytology in 6. A 15-mm skin incision was made above the sternal notch. The midline was opened and a 12-mm trocar inserted into the thyro-tracheal groove. It was inflated with CO2 for 3 min. The trocar was then removed and the procedure performed using external retractors and needlescopic instruments. The upper pedicle was dissected. Identification of recurrent nerve and parathyroid glands was facilitated by endoscopic magnification. The upper gland portion was then retracted out of the operative cavity; inferior veins were ligated and the lobe entirely extracted and dissected. Frozen section was obtained for "cold" nodules.

RESULTS

Video-assisted hemithyroidectomy was accomplished in 24 patients; 1 underwent video-assisted total thyroidectomy (positive frozen section). Cervicotomy was required once to achieve hemostasis and once to perform total thyroidectomy (positive frozen section). Mean operative time was 82 min (range 60-120 min). No complications were registered. The cosmetic result was excellent.

CONCLUSIONS

Video-assisted thyroid surgery is feasible and may improve cosmetic outcome; total thyroidectomy can be accomplished through the same access point.

Effects of hormonal replacement treatment on bone mineral density and metabolism in hypogonadal patients

We investigated 22 male patients affected by prepubertal hypogonadism with a mean age of 34.3+/-5.2. A significant reduction of bone mineral density (BMD) at both the lumbar spine (L2-L4, -14%, 1.039+/-0.11 vs. 1.217+/-0.16 g/cm(2), P=0.005) and femoral neck (-11%; 0.927+/-0.09 vs. 1.034+/-0.16 g/cm(2), P=0.01) was found in patients compared to age-matched controls. The mean Z score was -1. 55 for vertebrae and -1.33 for femur. Eleven and nine patients, respectively, had a lumbar and femoral BMD at least 1 S.D. below the normal mean; 8 and 4, respectively, 2 S.D. below. There was a strong positive correlation between BMD and duration of hormone replacement treatment (HRT) for both sites: respectively, r=0.71, P<0.005 for the vertebrae, and r=0.60, P<0.01 for the femur. A weak correlation was also present between onset of HRT and BMD: r=0.6, P<0.01 at the lumbar level, and r=0.47, P<0.05 at the femoral neck.

A novel mutation in the pendrin gene associated with Pendred's syndrome

OBJECTIVE

Pendred's syndrome is an autosomal recessive disorder characterized by goitre, sensorineural deafness and iodide organification defect. It is one of the most frequent causes of congenital deafness, accounting for about 10% of hereditary hearing loss. It is caused by mutations in the pendrin (PDS) gene, a 21 exon gene located on chromosome 7. The aim of this study was to examine an Italian family affected with Pendred's syndrome at the molecular level.

PATIENTS

Thirteen subjects belonging to a family from Southern Italy were evaluated for the clinical and genetic features of Pendred's syndrome.

MEASUREMENTS

Exons 2-21 of the PDS gene were amplified from peripheral leucocytes by the polymerase chain reaction; mutation analysis was performed by single strand conformation polymorphism, direct sequencing and restriction analysis.

RESULTS

The index patient had the classical triad of the syndrome and harboured two mutations in the PDS gene in the form of compound heterozygosity. He was found to be heterozygous for a cytosine to adenosine mutation at nucleotide 1523 in exon 13 and for a IVS 1001 + 1G --> A mutation. The former is a novel mutation which results in a change of 508 threonine to asparagine in the putative eleventh transmembrane domain. The latter mutation in the donor splice site has already been described in other patients and is thought to lead to aberrant splicing and premature protein truncation. Three subjects who were heterozygous for one mutation had normal phenotypes. Two subjects had sensorineural deafness and were heterozygous for a single mutation. Goitre was found only in patients with Pendred's syndrome and was absent in all other individuals, albeit residing in an iodine-deficient area.

CONCLUSIONS

We have identified a novel mutation in the pendrin gene causing Pendred's syndrome, and confirm that molecular analysis is a useful tool for a definitive diagnosis. This is particularly relevant in cases such as in the subjects of our family in which the clinical features might be misleading and other genetics factors might be responsible for deafness.

Pendrin does not increase sulfate uptake in mammalian COS-7 cells

Pendred's syndrome is characterized by goiter, sensorineural deafness and impaired iodide organification. It is one of the most frequent causes of congenital deafness accounting for about 10% of hereditary hearing loss. It is caused by mutations in the pendrin (PDS) gene, which was postulated to be a sulfate transporter, because of its homology with other genes. We tested sulfate transport in mammalian COS-7 cells that were transiently transfected with PDS cDNA. 35SO4 uptake increased in a time-dependent manner, but this phenomenon was similar in cells transfected with PDS and in mock-transfected cells (450 and 360 cpm/beta-gal units at 10 min, respectively; 38,250 and 31,000 cpm/beta-gal units, at 12 h, respectively). There was no significant increase in 35SO4 uptake using increasing amounts of PDS-containing plasmid (up to 12 microg per dish). These data indicate that pendrin is not a sulfate transporter. Additional functional studies on this protein are warranted to clarify its role in thyroid pathophysiology and inner ear development.