Thyroid Hormone Assays Research Articles

Altered patterns of thyroid hormones in serum and urine in pregnancy and during oral contraceptive therapy.

Serum total, percentage free fraction and absolute serum free hormone concentration of thyroxine and triiodothyronine were measured in control, pregnant and oral contraceptive users, together with the daily urinary losses of unconjugated thyroid hormones. Increased urinary losses of both hormones, in particular thyroxine, were apparent in pregnancy and these could not be explained in terms either of an increased filtered load of hormone or the presence of proteinuria. The possible existence of filterable small-molecular weight hormone-binding substances in the urine of pregnant patients is discussed. It is concluded that assay of urinary thyroid hormones during pregnancy is of limited diagnostic value because of overlap with thyrotoxic values.

Pituitary tumors in patients with secondary amenorrhea

This study was undertaken to determine the prevalence of radiologically detectable pituitary tumors among patients seen initially in a gynecology clinic for a complaint of secondary amenorrhea. In a group of 144 women with secondary amenorrhea of more than 6 months' duration, 13 had radiologic abnormalities of the sella turcica detectable with standard skull films without tomography. These gynecologic patients composed more than half of the women in the reproductive age group who were diagnosed at this medical center as having a pituitary tumor. Only one patient with oligomenorrhea or secondary amenorrhea of less than 2 years' duration had a detectable tumor. Thus, for patients with short-term amenorrhea, the risk of having a pituitary tumor is small, especially in the absence of galactorrhea, headache, or changes in vision. However, 12 of 71 patients with amenorrhea longer than 2 years (17 per cent) had detectable tumors and the risk appears to increase progressively with time. Assay of adrenal and thyroid hormones did not discriminate between patients with and without pituitary tumors. Early detection of these tumors is aided by serial sella x-rays, tomograms, prolactin assays, and newer pituitary function tests. Patients presenting with postpill amenorrhea and postpartum amenorrhea illustrate the hazard of interpreting a temporal relationship as a causal one.

Effect of halofenate on serum thyroid hormone determinations in vitro.

Halofenate has been shown to decrease thyroxine (T4) binding to thyroxine-binding globulin (TBG) in vitro. Several indirect serum thyroid hormone assays are dependent on thyroid hormone binding and the results might be altered by halofenate in the serum. Halofenate free acid (50-500 mug/ml) was added to serum samples in vitro, and the samples were assayed for total serum T4 by competitive protein-binding assay (CPB) and radioimmunoassay (RIA), the per cent of dialyzable T4 (%FT4), total serum triiodothyronine (T3) by RIA, and resin T3 uptake (RT3U). Halofenate increased the measured T4 (CPB), %FT4, T3 (RIA), AND RT3U, but did not alter the T4 (RIA) determination. Thus, halofenate appears to diminish T4 binding to TBG in vitro, and artifactually alters the serum determinations of T4 (CPB), %FT4, T3 (RIA), AND RT3U. Calculated values derived from these measurements for the free thyroxine index and "free" T4 will also be affected halofenate. Only the T4 (RIA) determination was unchanged by the presence of halofenate in vitro.

The assay of urinary thyroid hormones for assessing thyroid function.

A competitive protein binding assay for thyroxine (T-4) and a radioimmunoassay for tri-iodothyronine (T-3) were applied to determine the urinary concentrations of these hormones. These measurements were shown to offer excellent diagnostic discrimination between euthyroid, hypothyroid, and hyperthyroid subjects. Urinary T-3 and T-4 levels were not affected by changes in the concentration of thyroxine binding globulin (TBG) or by changes in binding capacity; and therefore, remained normal during pregnancy, oestrogen, and phenytoin therapy. There was no significant circadian variation in urine T-3 excretion. Thus T-3 assays of overnight urine samples could be used in conjunction with dynamic test procedures, such as thyrotrophin (TSH) stimulation test, to enable the rapid assessment of the integrity of the hypothalamic-pituitary-thyroid axis.

Frequency & pattern of malignancy in solitary thyroid nodule

This cross sectional study done in the department of Banghabandhu Sheikh Mujib Medical University and Dhaka Medical College Hospital during the period of July 2005 to October 2007 to determine frequency & pattern of malignancy in solitary thyroid nodule. For this study, 118 patients who were diagnosed as a case of malignancy in solitary thyroid nodule by detailed history, clinical examination, thyroid hormone assay, ultrasonogram, thyroid scan, FNAC and histopathological examination, were collected. In this study majority of the patients were within 21-40 years of age. Frequency of solitary thyroid nodule is more in female with male female ratio 1: 2.11 Majority of the nodules were firm (72.03%), others were hard (16.95%) and cystic (11.02%). Malignant lesion was more common in hard nodule (70%). Most of the nodules were cold (66.10%) among them 25.6% cases were malignant, followed by warm (30.5%) and hot (3.3%). No malignancy was found in hot nodule. FNAC showed colloid nodule (44%), cellular follicular lesion (29.66%), papillary carcinoma (12.7%), colloid degeneration (4.2%) and medullary carcinoma (1.6%) Out of 118 patients, histopathologically non malignant were 96 (81.35%) and malignant were 22(18.65%). Among malignant cases, 16 (72.72%) cases were papillary carcinoma, 4 (18.18%) cases were follicular carcinoma and 2(9.1%) cases were medullary carcinoma. Key words: Solitary thyroid nodule, FNAC, Papillary carcinoma, Follicular carcinomaDOI: 10.3329/bjo.v15i1.4303 Bangladesh J of Otorhinolaryngology 2009; 15(1): 1-5