A visual index of thyroid function

The utility of technetium-99m pertechnetate thyroid scintigraphy assessing thyroid/salivary ratio as an alternative to thyroid uptake percentage in evaluation of thyroid function, with establishing normal reference values of both parameters: single Egyptian center study

BACKGROUND/OBJECTIVE

Management of thyroid disorders depends on accurate clinical assessment, appropriate investigations and radionuclide imaging, which plays an established important role either qualitatively or quantitatively. The aim of this study was to assess the utility of the thyroid/salivary ratio (TSR) as an alternative to technetium-99m (Tc99m) pertechnetate thyroid uptake (TcU) percentage in the evaluation of thyroid function and in the same time to establish reference range for the thyroid uptake of Tc99m-pertechnetate and TSR among Egyptian populations.

PATIENTS AND METHODS

This retrospective study enrolled 270 patients, out of which 250 with different thyroid disorders and 20 without thyroid diseases, as a control group who all underwent full clinical examination, thyroid function tests and Tc99m pertechnetate thyroid scintigraphy. The TcU percentage and TSR were calculated and then correlated to the thyroid hormonal profile.

RESULTS

The normal reference ranges of TcU and TSR were 0.75-3.5% and 1.25-4.8%, respectively. The sensitivity and specificity of TSR to diagnose hyperthyroidism were slightly lower compared with TcU (84.5 and 92.3% vs. 86.2 and 98.3%, respectively) at TSR cutoff value of more than 4.8 and TcU cutoff value of more than 3.5. Meanwhile, they had comparable sensitivity and specificity to diagnose hypothyroidism (86.0 and 93.3% vs. 86.5 and 94.5%) at cutoff values <0.75 and <1.25, respectively.

CONCLUSION

The current study established a reference range for TcU and TSR in our institution. TSR is comparable to TcU in the evaluation of thyroid function among hyper-and hypothyroid patients and TSR can be used in doubtful cases of mal-thyroid function for confirmation of the diagnosis.

Animal models of disease: feline hyperthyroidism: an animal model for toxic nodular goiter

Since first discovered just 35 years ago, the incidence of spontaneous feline hyperthyroidism has increased dramatically to the extent that it is now one of the most common disorders seen in middle-aged to senior domestic cats. Hyperthyroid cat goiters contain single or multiple autonomously (i.e. TSH-independent) functioning and growing thyroid nodules. Thus, hyperthyroidism in cats is clinically and histologically similar to toxic nodular goiter in humans. The disease in cats is mechanistically different from Graves' disease, because neither the hyperfunction nor growth of these nodules depends on extrathyroidal circulating stimulators. The basic lesion appears to be an excessive intrinsic growth capacity of some thyroid cells, but iodine deficiency, other nutritional goitrogens, or environmental disruptors may play a role in the disease pathogenesis. Clinical features of feline toxic nodular goiter include one or more palpable thyroid nodules, together with signs of hyperthyroidism (e.g. weight loss despite an increased appetite). Diagnosis of feline hyperthyroidism is confirmed by finding the increased serum concentrations of thyroxine and triiodothyronine, undetectable serum TSH concentrations, or increased thyroid uptake of radioiodine. Thyroid scintigraphy demonstrates a heterogeneous pattern of increased radionuclide uptake, most commonly into both thyroid lobes. Treatment options for toxic nodular goiter in cats are similar to that used in humans and include surgical thyroidectomy, radioiodine, and antithyroid drugs. Most authorities agree that ablative therapy with radioiodine is the treatment of choice for most cats with toxic nodular goiter, because the animals are older, and the disease will never go into remission.

Sonographic diagnosis and grading of Hashimoto's thyroiditis

There is no ideal test for the diagnosis of Hashimoto's thyroiditis (HT). The purpose of this study was to determine the type of information sonography provides in these patients. In 47 cases of HT we identified four distinct sonographic patterns which correlated with degree of disease severity. The higher patterns had larger glands, higher antithyroid antibody titers, lower T4 and higher TSH levels, and higher incidence of hypothyroidism. With sonography we were able to suspect the diagnosis in patients with goiter of unknown etiology, to measure gland size, identify patients with functional impairment, and predict which patients required treatment. No other single test provides so much information in patients with HT.