Graphene Oxide's Reduction of Hydrolytic Degradation in Polyamide-11.

Graphene oxide (GO) was incorporated into polyamide-11 (PA11) via in-situ polymerization. The GO-PA11 nano-composite had elevated resistance to hydrolytic degradation. At a loading of 1 mg/g, GO to PA11, the accelerated aging equilibrium molecular weight of GO-PA11 was higher (33 and 34 kDa at 100 and 120 °C, respectively) compared to neat PA11 (23 and 24 kDa at 100 and 120 °C, respectively). Neat PA11 had hydrolysis rate constants (kH) of 2.8 and 12 (×10-2 day-1) when aged at 100 and 120 °C, respectively, and re-polymerization rate constants (kP) of 5.0 and 23 (×10-5 day-1), respectively. The higher equilibrium molecular weight for GO-PA11 loaded at 1 mg/g was the result of a decreased kH, 1.8 and 4.5 (×10-2 day-1), and an increased kP, 10 and 17 (×10-5 day-1) compared with neat PA11 at 100 and 120 °C, respectively. The decreased rate of degradation and resulting 40 % increased equilibrium molecular weight of GO-PA11 was attributed to the highly asymmetric planar GO nano-sheets that inhibited the molecular mobility of water and the polymer chain. The crystallinity of the polymer matrix was similarly affected by a reduction in chain mobility during annealing due to the GO nanoparticles' chemistry and highly asymmetric nano-planar sheet structure.

[Multinodular goitre: not always harmless]. / Multinodulair struma: niet altijd onschuldig.

Multinodular goitre has a slow and progressive growth. The clinical presentation of patients with multinodular goitre is variable and dependent on size, location and the functional state of the thyroid tissue. The most frequent clinical symptoms are caused by compression and deviation of the trachea and range from dyspnoea to acute asphyxia. Imaging is important to confirm the size of the multinodular goitre. Timing of the treatment can be critical. However, a good treatment guideline is lacking. There are two treatment options: radioactive iodine and surgical resection. The best treatment option and timing of treatment for patients with multinodular goitre should be assessed and decided on an individual basis. In this clinical report we present two patients who had a multinodular goitre with progressive symptoms for years. Patient A, 66 years of age, was successfully treated with radioactive iodine. Patient B, 77 years of age, underwent a total thyroidectomy.

[Addison's disease, primary adrenal insufficiency in adults]. / De ziekte van Addison. Primaire bijnierschorsinsufficiëntie bij volwassenen.

Adrenal insufficiency is a rare but fatal disease if left unrecognized. Symptoms often mimic more prevalent diseases. We discuss three patients with primary adrenal insufficiency. These cases illustrate that presenting symptoms such as syncope, nausea, vomiting, weight loss and hypoglycemia are often non-specific and, therefore, often not immediately recognized. When an adrenal crisis is suspected, glucocorticoids should be given promptly. The symptoms are caused by insufficient production of adrenal hormones due to destruction of the adrenal glands by auto-immune adrenalitis. An ACTH stimulation test should confirm the diagnosis when primary adrenal insufficiency is suspected. Treatment consists of glucocorticoid and mineralocorticoid replacement. Primary adrenal insufficiency is a 'master of disguise'. Unexplained syncope, vomiting, weight loss or hypoglycemia should prompt suspicion of this disease.

Variation in phenotypic appearance of Graves' disease: effect of genetic anticipation and duration of complaints.

OBJECTIVE: Both genetic and environmental factors contribute to susceptibility of Graves' disease. In this study, we evaluated whether the duration of symptoms or a positive family history of autoimmune thyroid disease (AITD) are related to specific phenotypes in patients with a first episode of Graves' hyperthyroidism (GH). DESIGN: Cross-sectional multicentre observational study. PATIENTS: Two hundred and sixty-three consecutive untreated patients (mean age (+/-s.d.) 42.6+/-12.4 years; range 16-79 years) with a first episode of GH were included. Biochemical and clinical severity of GH was evaluated. Participants were asked to complete questionnaires about environmental factors (smoking behavior, use of estrogens, stress etc.), the duration of symptoms (interval between start of symptoms and date of referral) and family history for AITD. We ascertained the autoimmune nature of thyroid disease in affected relatives. Family history scores (FHS; high score indicating a close genetic relationship and/or a large number of affected relatives) were calculated for patients with a positive family history for AITD. RESULTS: The peak incidence for the diagnosis of GH was 2-3 months after onset of symptoms (32% of patients). Duration of symptoms was negatively associated with age (P for trend=0.04). A positive family history for AITD was present in 42.6% of patients. Patients with the highest FHS were more often male (P=0.01) while age at onset was lower (P=0.02) compared to patients with a lower FHS. Among patient groups with different FHS, no differences were found in exposure to environmental factors, nor in clinical or biochemical severity of hyperthyroidism. CONCLUSION: Our study does not support the hypothesis that a short duration of thyrotoxic symptoms until diagnosis is related to more severe hyperthyroidism in Graves' disease. We have found supporting evidence for the existence of genetic anticipation in Graves' disease by means of a lower age of onset in the group with the highest FHS.

Age and stress as determinants of the severity of hyperthyroidism caused by Graves' disease in newly diagnosed patients.

OBJECTIVE: The evidence that stress may provoke Graves' hyperthyroidism in genetically susceptible subjects is substantial. Whether exposure to stress is related to the severity of thyrotoxicosis has not been studied. Advancing age is associated with not only less severe Graves' hyperthyroidism but also self-reported stress. We tested the hypothesis whether advancing age is associated with less exposure to stress, resulting in a lower immunological response, and less severe Graves' hyperthyroidism. DESIGN: Cross-sectional multicenter study. PATIENTS: Two hundred and sixty-three consecutive untreated patients with a first episode of Graves' hyperthyroidism were included. The severity of Graves' hyperthyroidism was evaluated biochemically (freeT(4)-index and freeT(3)-index, thyrotropin-binding inhibitory immunoglobulin (TBII)) and clinically by the hyperthyroid symptom scale score (HSS score). Stress exposure was quantitated by three questionnaires. RESULTS: Advancing age was associated with less severe Graves' hyperthyroidism, both biochemically by lower serum freeT(3)-index and freeT(4)-index (P<0.01), lower serum TBII (P=0.05), and clinically by lower HSS scores (P=0.04) and smaller goiter size (P<0.01). FreeT(3)-index and freeT(4)-index were directly associated with HSS scores (P<0.01). Stress scores were associated with HSS scores (P<0.01) but not with biochemical severity of Graves' hyperthyroidism. Advancing age was associated with lower scores for stress exposure. Multivariate regression analysis showed that HSS score was independently related to the tendency to report negative feelings (P<0.01) but not to other stress scores and also not to age. CONCLUSION: Advancing age is associated with less exposure to stress, lower serum TBII and less severe clinical and biochemical Graves' hyperthyroidism. Because no direct relationship exists between stress exposure and TBII or freeT(3)-index and freeT(4)-index, we reject our hypothesis that less stress is causally related to biochemically less severe Graves' hyperthyroidism in old age. HSS score is primarily determined by negative feelings and not by age.

Frequency and characteristics of TBII-seronegative patients in a population with untreated Graves' hyperthyroidism: a prospective study.

OBJECTIVE: It is claimed that second generation thyrotropin-binding inhibitory immunoglobulin (TBII) assays have a very high sensitivity for the diagnosis of Graves' hyperthyroidism (GH). However, studies evaluating the accuracy of TBII have been retrospective in nature and/or GH had not been diagnosed independently of TBII. The aim of the present study, therefore, was to prospectively evaluate the frequency and characteristics of TBII-seronegative patients in a population of untreated GH diagnosed independent of serum TBII. DESIGN: Prospective multicentre observational study. PATIENTS: A total of 259 consecutive untreated patients with a first episode of GH, diagnosed independent of serum TBII. TBII levels were measured by second generation assay and correlated to thyroid function, clinical characteristics and exposure to environmental factors. RESULTS: Serum TBII was positive in 245 (94.6%) patients and negative (< 2 IU/l) in 14 (5.4%) patients. TBII-seronegative patients had lower fT4 (median 42.5 vs. 53.9 pmol/l, P = 0.02), T3 (median 3.55 vs. 4.90 nmol/l, P < 0.01) and fT3-index (median 4.30 vs. 6.27, P < 0.01) compared to TBII-seropositive patients. None of the TBII-seronegative patients had TSH-receptor activating mutations, Graves' orbitopathy or pretibial myxedema. Serum TBII was positively correlated to free T3 (fT3)-index and free T4 (fT4)-index (P < 0.01), goitre size (P < 0.01) and the prevalence of Graves' orbitopathy (P < 0.01). There were no significant differences between TBII-seropositive and TBII-seronegative patients in environmental factors. CONCLUSION: The prevalence of TBII-seronegativity in untreated patients with GH is 5.4% using a second generation assay. TBII-seronegative patients have biochemically less severe thyrotoxicosis and no Graves' orbitopathy. TBII-seronegative and TBII-seropositive patients apparently belong to the same population of GH, albeit the severity of the autoimmune attack is less in TBII-seronegative patients.