Thyroidology最新文献

In iodine rich areas the incidence of papillary carcinoma of the thyroid is extremely high but its prognosis is favorable. When papillary carcinoma is confined to one lobe, our standard surgical procedure has been total lobectomy with isthmusectomy rather than total thyroidectomy. Our followup study of 185 such patients reveals considerable difference in the outcome between the 85 patients with gross thyroid capsular invasion and the 100 patients without, regardless of the presence of cervical lymph node metastasis. In the latter group, the tumor could be completely resected in all patients; although 4 cases had recurrence and required reoperation, 3 patients are alive and well and one died of other disease. In contrast, 20 patients in the former group had incomplete resection of the tumor, 4 patients developed recurrence and needed to be reoperated and 7 patients eventually died of thyroid cancer. One hundred thirty three patients (71.9%) underwent modified neck dissection at the time of surgery to find lymph node metastasis in 37 of 59 cases (62.7%) without gross thyroid capsular invasion and 64 of 74 cases (86.5%) with such invasion. The difference is statistically significant (P < 0.05). From these results we conclude that for papillary thyroid cancer in iodine rich areas total lobectomy with isthmusectomy is the treatment of choice when gross thyroid capsular invasion is not recognized on the operation table. However, when gross thyroid capsular invasion is recognized, total or near total thyroidectomy has to be performed.

In a retrospective study of 27 cases of iodine deficiency and/or latent primary hypothyroidism and in 16 cases of thyroid adenoma with hyperthyreosis the routine radioiodine uptake test was combined with a protirelin (TRH) test. After TRH infusion, [PB*I] and TSH increased significantly in all of these 27 patients who served as controls for the hyperthyroid patients. At the same time, the conversion rate Q rose in 14 of the control patients, but it dropped in 13 cases, thus indicating a TSH-induced discharge from the thyroid of radioiodine containing substances that were not bound to serum proteins. In nine of the 16 patients with autonomous adenoma, PB[*I] rose slightly, but Q did not increase significantly. In seven of the 16 adenoma patients, both PB[*I] and Q even dropped slightly in the absence of measurable serum TSH, thus indicating a negative direct effect of TRH on thyroid hormone metabolism.

Since the late sixties standard total thyroidectomy with or without selective radical neck dissection depending on the extent of the disease has become the routine surgical procedure for differentiated thyroid carcinoma (DTC;-papillary, follicular). This strategy has contributed remarkably to the increase of cure rates for various reasons. Only recently, in the last decade, has limited radicality with only unilateral lobectomy (= hemithyroidectomy) with or without partial contralateral resection been advocated as being sufficient for selected early tumor stages. We have analyzed a series of 252 patients, 174 (69%) being papillary and 78 (31%) follicular. Primary operation was done in 117 patients (46%) while 135 patients (54%) underwent reoperative surgery at this institution for either completion of radicality or because of loco-regional recurrence. From our evaluation we draw the conclusion that limited radicality (unilateral operation or subtotal) is justified only in pT-1-tumors in younger age (< 45 yrs) in order to avoid recurrence and unnecessary reoperation. On the other hand generous indication for reoperation is justified with the overall chance of almost 60% cure rate. All adjuvant treatment, mainly radioiodine should be applied thereafter.

Two patients are described in whom the absorption of l-thyroxine was impaired by non-prescription herbal and nutritional remedies. The absorption of thyroid hormones is discussed and an approach to the problem of patients who appear to be unresponsive to the usual doses of thyroid hormones is suggested.

While some may still favor lobectomy, most experts recommend total thyroidectomy for DTC followed by radioablation of thyroid remnant with 131I. After such a treatment, serum Tg level serves as a useful marker of metastases of DTC. Radioiodine (131I) is a reasonable good treatment for small (mg in weight) deposits of metastases. However, large lesions, and those in the lungs and bones, do not respond well to clinically "safe" doses of 131I. Some experts suggest that employment of radiation dose based approach to 131I may improve the outcome of treatment of DTC. Agents that enhance the sensitivity of the tissues to radiation effects of 131I should be helpful and research needs to be encouraged in that area.

In this review it is concluded that thyroxine (T4), triiodothyronine (T3) and iodine (KI), singly or in combination, are all effective in reducing the goiter size, but there is insufficient evidence to prove which is the best (possibly the combination of T4 + KI?). Higher doses are more effective than smaller, but also lead to more side-effects. Thus, the optimal dose has yet to be found. The suppression of the pituitary thyroid axis plays a major role in the treatment of non-toxic goiter, but it is not definite that this is the only mechanism responsible for the beneficial effect of the agents mentioned. In view of the lack of better evidence, it is simply suggested that non-toxic goiters in young persons should be initially treated aggressively with 200 micrograms of T4/day or more for some months. If the goiter shrinks then the dose should be gradually decreased. If the goiter persists, it is futile to continue with large doses for more than 6-12 months. One may continue with smaller doses, maintaining the serum TSH in the low-normal range. The treatment of benign thyroid nodules with thyroxine is controversial. Probably thyroxine is beneficial in about a third of the cases. For both non-toxic goiters and nodules, autonomy should be excluded before starting thyroxine treatment, and old age, cardiac disease and a poor general condition are contraindications.

Most of the circulating T3 is generated by monodeiodination of T4 in extrathyroidal tissue with only minor contribution by the thyroid gland. Since T3 is the main active thyroid hormone and TSH is the major modulator of its synthesis and release by the thyroid gland, TSH may also play a significant role in synthesis and release of T3 by the peripheral tissues as documented in recent in vitro animal studies. However, the data regarding its influence on T4 metabolism in humans is lacking. Hypothyroidism may provide an appropriate environment for assessing the influence of TSH in synthesis and release of T3 by the extrathyroidal tissues, since circulating T3 is almost totally derived via peripheral conversion of T4, and serum TSH varies from subnormal levels in central hypothyroidism to a wide range of supernormal concentration in the primary variety. This study determined the relationship between serum TSH concentration and T3 and T4 ratio, a reliable index of conversion of T4 into T3 in peripheral tissues, in 75 subjects with hypothyroidism including both the primary and the central types. Serum T3 was significantly higher (p < 0.001) in primary hypothyroidism (1.48 +/- 0.13 mM/l) in comparison with the central type (0.71 +/- 0.09 mM/l) despite almost equally low serum T4 concentration in both groups. In primary hypothyroidism, T3:T4 ratio (0.026 +/- 0.0012) was significantly higher (p < 0.01) than normal (0.017 +/- 0.0010) along with supernormal TSH (71 +/- 6.4 mU/L) concentration prior to initiation of LT4 replacement therapy and normalized (0.015 +/- 0.0008) on achieving euthyroid state with correction of serum TSH level (3.8 +/- 0.3 mU/L).(ABSTRACT TRUNCATED AT 250 WORDS)

A case of a man with thyroid cancer who ingested between 0.9 and 3.3 mg l-thyroxine per day for over 10 years (the highest dose for 3 years) is reported. This had been prescribed for suppression of TSH for a well differentiated thyroid cancer. He was essentially asymptomatic and suffered no apparent ill effects from this prolonged and markedly excessive dosage of l-thyroxine. The literature lists a wide range of ill effects from both chronic and acute thyroid hormone overdosage but also records many examples of tolerance to excessive levels of exogenous thyroid hormone. The various circumstances leading to thyroid hormone overdose and potential ill-effects are reviewed.

Human thyroglobulin pretreated with iodine (1mM) at alkaline pH is split to small molecular weight fragments after reduction with dithiothreitol. Iodine pretreatment alone did not induce any changes in the thyroglobulin molecular weight.

Serum thyroid stimulating hormone (TSH) levels were measured in 127 patients with varying grade of chronic renal failure (CRF). Sensitive immunoradiometricassays (IRMA) were used so that small changes in TSH levels if any, could be appreciated, and to see if such alterations exhibit some relationship with those in thyroid hormone levels. Mean serum TSH levels in the patient group of 2.33 microU/ml (0.07-7.3) was significantly higher in comparison to 1.73 microU/ml (0.25-4.6) in normal subjects (p < 0.001). However, they were not significantly different when measured by radioimmunoassay (RIA) as compared to normals. Serum triiodothyronine (T3), thyroxine (T4) and free triiodothyronine (FT3) levels of 72 +/- 32 ng/dl, 7.4 +/- 2.6 micrograms/dl and 2.9 +/- 0.9 pg/ml were significantly lower than in normal subjects, whereas serum free thyroxine (FT4) showed a slight though not significant elevation. When patients were divided in three subgroups according to the degree of renal insufficiency, TSH levels showed a gradual rise with corresponding depression in their T3, FT3 and T4 levels. In 19 patients who were on hemodialysis (HD) and subsequently received successful renal transplantation, most of the thyroid function parameters returned towards the normals with TSH undergoing significant depression from their pretransplant levels as well as from normal levels. The results indicated that a slight but significant elevation in TSH levels could be revealed by sensitive IRMA in patients with CRF. Rising TSH levels with increasing renal insufficiency and its inverse relationship with T3 and T4 levels suggest maintenance of pituitary thyroid axis.(ABSTRACT TRUNCATED AT 250 WORDS)