Dietary Management of Hyperthyroidism in a Dog.

An 8 yr old female spayed golden retriever presented for a routine exam during which ventral cervical soft tissue masses were identified. History included weight loss, increased activity and appetite, gagging, and occasional diarrhea. Exam findings included a body condition score of 4/9 and palpable ventral cervical nodules. A serum thyroxine (T4) value was 8.0 ug/dL (normal = 0.8-3.5ug/dL). Doppler systolic blood pressure readings ranged from 200-210 mmHg (normal systolic blood pressure <150 mmHg). The diagnosis was hyperthyroidism due to active thyroid masses. Due to financial constraints, the owner elected conservative management. Initial treatment with methimazole resulted in a decreased T4 value of 5.0 ug/dL at approximately 4 mo after initiation of treatment. A commercially available iodine-restricted feline diet was fed and this resulted in further reduction in serum T4 levels, improved sleeping cycles, reduced anxiety, and reduced systolic blood pressure. A temporary suspension of iodine-restricted feline diet for 2 mo resulted in increases in serum T4 concentrations, which, subsequently, decreased with re-introduction of the diet. Roughly 10 mo after initiation of the therapeutic diet and 16 mo after intial diagnosis, the dog remains relatively normal clinically despite active growing cervical masses with T4 concentration of 2.3 ug/dL.

Effect of Selenium Supplementation on Recurrent Hyperthyroidism Caused by Graves' Disease: A Prospective Pilot Study.

The effect of selenium supplementation on recurrent hyperthyroidism caused by Graves' disease is unclear. Our study aimed to assess the efficacy of selenium supplementation therapy on recurrent Graves' disease. Forty-one patients with recurrent Graves' disease were enrolled in this study. All patients received the routine treatment using methimazole (MMI), while patients allocated to the selenium group received additional selenium therapy for 6 months. The influence of selenium supplementation on the concentrations of thyroid stimulating hormone (TSH), anti-TSH-receptor antibodies (TRAb), free thyroxine (FT4), and free triiodothyronine (FT3) were assessed. The remission rate was also compared between 2 groups. There was no obvious difference in the demographic data and the levels of serum FT4, FT3, TSH, and TRAb between the 2 groups at baseline. Both FT4 and FT3 decreased more at 2 months in the selenium group than the controls, while the TSH level increased more in patients receiving selenium supplementation (p<0.05). The TRAb level was significantly lower in patients receiving selenium supplementation (2.4 IU/l vs. 5.6 IU/l, p=0.04). The percentages of patients with normal TRAb level at 6 months was also significantly higher in the selenium group (19.0 vs. 0%, p=0.016). Kaplan-Meier survival curve showed patients receiving selenium supplementation had a significantly higher rate of remission than controls (Log-rank test p=0.008). In conclusion, selenium supplementation can enhance the effect of antithyroid drugs in patients with recurrent Graves' disease. Randomized trials with large number of participants are needed to validate the finding above.

Effect of a Limited Iodine Diet on Iodine Uptake by Thyroid Glands in Hyperthyroid Cats.

BACKGROUND: The effect of feeding a limited iodine diet on radioactive iodine uptake in the thyroid glands of hyperthyroid cats is unknown. OBJECTIVES: To determine how feeding limited dietary iodine affects radioactive iodine uptake by the thyroid glands of hyperthyroid cats. ANIMALS: Eight geriatric cats with spontaneous hyperthyroidism. METHODS: Prospective study of eight client owned hyperthyroid cats fed a commercially available iodine limited diet for 6 months. Clinical signs were evaluated and TT4 and fT4 were measured during consumption of the diet. Uptake of (123)I was determined before and 8-16 weeks after exclusive consumption of the diet. RESULTS: Clinical signs of hyperthyroidism resolved in all cats, but there was no significant increase in body weight. TT4 and fT4 decreased into the reference range by 8-16 weeks in all cats. Mean TT4 before consumption of the diet was 9.7 µg/dL (SD 5.2) and after consumption of the diet was 3.1 µg/dL (SD 0.9). Scintigraphy revealed unilateral uptake of isotope in 5 cats and bilateral uptake in 3 cats. Mean percentage uptake of (123)I by the thyroid gland at 8 hours after isotope administration was 16.2 (SD 11.8) before diet consumption and 34.6 (SD 11.7) 8-16 weeks after exclusive consumption of the diet. The percentage increase was variable between cats (38-639%). CONCLUSIONS AND CLINICAL IMPORTANCE: Limited iodine diets increase iodine uptake in the autonomous thyroid glands of hyperthyroid cats. Further studies are necessary to determine if consumption of a limited iodine diet changes sensitivity of the thyroid gland to (131)I treatment.

Effect of Feeding an Iodine-Restricted Diet in Cats with Spontaneous Hyperthyroidism.

BACKGROUND: Exclusive feeding of an iodine-restricted diet has been proposed as a method for controlling clinical manifestations of hyperthyroidism in hyperthyroid cats. OBJECTIVES: To determine the effect of feeding an iodine-restricted diet on TT4 concentrations and clinical signs in cats with spontaneous hyperthyroidism. ANIMALS: Forty-nine client-owned cats with spontaneous hyperthyroidism. METHODS: Retrospective case series. Hyperthyroid cats were exclusively fed a commercially available iodine-restricted diet. Clinical response was assessed by change in weight and heart rate and serum TT4, blood urea nitrogen (BUN), and creatinine concentrations at various times during dietary management (21-60 days, 60-180 days). RESULTS: Serum TT4 normalized in 20/48 cats (42%) and 39/47 cats (83%) at 21-60 days and 61-180 days, respectively. Cats in which the TT4 concentrations were still above reference range at 21-60 days had a significantly higher starting TT4 than those that normalized their TT4 levels during the same time period (P = .038). Body weight did not significantly increase (P = .34) nor heart rate decrease (P = .64) during the study. There was a significant decrease in serum creatinine (P = .028). Cats in the low reference range for serum TT4 concentrations did not have a significant increase in body weight (P = .41) nor creatinine (P = .54) when compared to those with high reference range. CONCLUSIONS AND CLINICAL IMPORTANCE: Restricted-iodine diets were effective at maintaining serum TT4 concentrations within reference ranges for a majority of cats with spontaneous hyperthyroidism over 1 year, although not all clinical signs of hyperthyroidism improved.

Dietary management of feline endocrine disease.

When treating cats with endocrine disease, most veterinarians concentrate on medical or surgical treatments that can be used to manage or cure the disease. Dietary issues are frequently ignored or not properly addressed. However, nutritional support can play an integral role in the successful management of feline endocrine diseases. Furthermore, because most cats with endocrine disease are senior or geriatric, they may also have concurrent health conditions that warrant dietary intervention. This article discusses recommendations for nutritional support of the 2 most common endocrine problems of cats seen in clinical practice: hyperthyroidism and diabetes mellitus.

Effects of an iodine-restricted food on client-owned cats with hyperthyroidism.

The objective of this prospective, multicentre, non-controlled, open-label study was to evaluate the effects of an iodine-restricted food on circulating total thyroxine (TT4) concentrations and clinical parameters in client-owned cats with hyperthyroidism. Two hundred and twenty-five cats were enrolled in the study and adapted to the iodine-restricted food. Data from physical examinations, questionnaires completed by veterinarians and owners, and circulating concentrations of TT4, urea and creatinine were recorded at weeks 0, 4 and 8. The study group included 136 female and 89 male cats (median age 15 years, range 4-21 years). Group 1 (n = 113) had been on previous anti-thyroid medication, while group 2 (n = 112) consisted of newly diagnosed cats. No differences were found between the two groups at any time point. Circulating TT4 concentrations had decreased (P <0.0001) at week 4 and did not change significantly from week 4 to week 8. Circulating TT4 concentration was within the reference range in 56/88 cats at week 4 and in 51/68 cats at week 8. Clinical parameters (vomiting, polyuria, polydipsia, hyperactivity, polyphagia, weight loss, hair coat quality, and quality of life) had improved (P <0.0001) by week 4. Circulating creatinine concentration decreased (P = 0.001) from week 0 to week 4. Side effects associated with feeding the iodine-restricted food were not observed. In conclusion, in client-owned cats with hyperthyroidism an iodine-restricted food is a valuable management option to normalise circulating TT4 concentrations, and improve clinical signs of hyperthyroidism within 4 weeks. This applies to newly diagnosed cats, as well as to previously diagnosed cats receiving anti-thyroid drugs.

Optimization of iodine intake in Belgium.

Mild iodine deficiency (MID) is a long-standing problem in Belgium and was recognized only recently as public health issue by the Ministry of Health (MOH). The main MID-related health problems in Belgium are a high prevalence of thyroid nodules and multinodular goiter. The economic cost of thyroid nodular disease only in Belgium was estimated at about €40 millions per year. The Belgian health authorities adopted a selective strategy to optimize iodine intake through the fortification of bread with iodized salt. A progressive, step-by-step increase of the iodine content of salt was chosen in order to minimize the incidence of hyperthyroidism. MOH monitors this strategy by assessing periodically the urinary iodine concentration in school-aged children and pregnant women, as well as by a yearly follow-up of TSH concentrations in all Belgian newborns. Although the implementation of this strategy was an important step, the main drawback of the current situation is the absence of a legal framework to support the strategy. The utilization of iodized salt in bread on a voluntary basis was endorsed by the bakery industry and MOH. However a legal framework is required to assure the effectiveness and continuity of the program and to avoid a higher than optimal iodine intake in the population.

Effects of propylthiouracil on intestinal transit time and symptoms in hyperthyroid patients.

BACKGROUND/AIMS: Gastrointestinal disturbances such as diarrhea and malabsorption with steatorrhea may show up in hyperthyroid patients. The aim of our study was to evaluate oro-caecal transit time (OCTT) and gastrointestinal symptoms in hyperthyroid patients before and after propylthiouracil administration. MATERIALS AND METHODS: Twenty hyperthyroid patients (15 Females and 5 Males, mean age 47 years) were studied. Eight of them had diarrhea and 10 steatorrhea. The control group was composed of 20 healthy volunteers (13 F and 7 M, mean age 49 yrs). OCTT and fecal fat excretion were measured before and after propylthiouracil administration (300 mg/day for 10 day and then 200 mg/day for 30 days). RESULTS: Before the treatment in hyperthyroid patients had began the mean OCTT was significantly lower than in the control group (64 min. versus 107 min; p < 0.0001). After treatment mean OCTT became similar to the controls (p = ns); diarrhea disappeared in all affected patients and mean fecal fat excretion was reduced from 7.9 gr/24h to 3.4 gr/24h, with a statistically significantly difference (p < 0.0001). CONCLUSIONS: The treatment with propylthiouracil induces the normalization of thyroid hormone status and consequently of OCTT with the disappearance of gastrointestinal symptoms, such as diarrhea and steatorrhea, with a better efficacy if compared to other drugs utilized in the treatment of hyperthyroidism.

Plasmapheresis: an adjunct to medical management of severe hyperthyroidism.

A woman with hyperthyroidism and myasthenia gravis developed respiratory failure in association with radiation-induced thyroiditis. Treatment with steroids, propylthiouracil, propranolol, iodine, and plasmapheresis was associated with dramatic reduction in serum triiodothyronine (T3), serum thyroxine (T4), and thyroglobulin levels and prompt recovery of the patient. The medications that this patient received have been shown to cause an abrupt decline in serum T3 levels with little or no effect on the serum T4 concentration. The 56% decline in serum T4 observed in this patient during the first 24 hours of therapy suggests that plasmapheresis may be a useful adjunct to medical therapy in selected patients with severe hyperthyroidism.