Hyperthyroidism in the elderly

In 65 elderly hyperthyroid patients (age range 50-78 years), sex differences, signs and symptoms and thyroid function were studied and the data were compared with those on 48 young hyperthyroid patients (age range 20-29 years). The incidence of hyperthyroidism was 3.5 times higher in females than in males among the young patients, whereas it was approximately equal in males and females among the elderly patients. Signs and symptoms conformed with the textbook description in the young subjects but not in the elderly ones. Measurements of serum triiodothyronine (T3) and thyroxine (T4) proved useful in preventing false diagnoses in elderly patients with atypical symptoms. In some elderly subjects with marginal increases of serum T3 and T4 concentrations, measurement of serum thyroid-stimulating hormone (TSH) after administration of thyrotropin-releasing hormone (TRH) was required to achieve an accurate diagnosis. Serum T3 and T4 levels and the thyroidal uptake of radioiodine were slightly but not significantly lower in the elderly than in the young patients. A high titer of circulating thyroid auto-antibody in the elderly may be related to this slight decrease in thyroid function. Serum T3 levels were significantly lower in the elderly than in the young subjects; this suggests impairment of peripheral monodeiodination of T4. Any abnormal serum levels of T4, T3, and TSH before and after administration of TRH could easily be restored to normal by treatment with antithyroid drugs in the elderly patients.

Gaucher-like cells in juvenile GM1-gangliosidosis and in beta-thalassemia -- A histochemical and ultrastructural observation

Peculiar storage cells appearing in bone marrow aspirates from a patient with juvenile GM1-gangliosidosis and from one with beta-thalassemia were examined light microscopically, histochemically and electron microscopically. Light microscopically, most of the storage cells closely resembled Gaucher cells pathognomonic for Gaucher's disease. The cytoplasm of the Gaucher-like cells contained numerous variable-shaped membrane-bound inclusions mostly arranged in a mosaic pattern and filled with fibrillar materials. Intermingled tubular structures were usually narrow as compared to those of the Gaucher cells. These ultrastructural differences of the stored materials between the Gaucher-like cells and Gaucher cells were more clearly substantiated by the high resolution electron microscopy with negative staining technique. Enzyme cytochemically, acid phosphatase activity was proved in or around the storage inclusions, suggesting their lysosomal origin. Histochemically, it might be suggested that the stored materials of the Gaucher-like cells in juvenile GMI-gangliosidosis were non-sulfated acid mucopolysaccharides and glycopeptides, whereas glycoproteins were the major component of the storage cells in beta-thalassemia. Possible mechanisms of storage in the Gaucher-like cells were discussed in both disorders.

Difference in pituitary-thyroid feedback regulation in hypothyroid patients, depending on the severity of hypothyroidism

In an attempt to study pituitary-thyroid interplay during replacement therapy for hypothyroidism, T4 (75-150 micrograms/day) was administered for at least 3 months. A small dose of T4 (75 micrograms/day) significantly depressed basal and TRH-stimulated TSH levels in normal subjects without significantly elevating serum T4 and T3 concentrations. In patients with severe hypothyroidism and marked enlargement of the sella turcica, T4 (2.53 micrograms/kg BW) normalized the serum T4 and slightly elevated the serum T3 but failed to normalize basal and TRH-stimulated TSH levels. In patients with moderate hypothyroidism and moderate enlargement of the sella turcica, T4 (2.0 micrograms/kg BW) normalized serum T4, T3, and basal TSH concentrations but failed to normalize TRH-stimulated TSH levels. In patients with slight hypothyroidism and slight enlargement of the sella turcica, T4 (1.84 micrograms/kg BW) normalized serum T4, T3, and TSH (both basal and TRH stimulated) concentrations. In five patients, an apparent paradoxical increase of basal serum TSH level was found shortly after starting thyroid hormone treatment. It is suggested that pituitary-thyroid interplay during the first 3-6 months of replacement therapy for hypothyroidism varies greatly depending on the severity of hypothyroidism.

An increase of liver uptake of thyroxine, an initial step of an increased fecal loss of thyroxine in response to propylthiouracil in rats

Propylthiouracil augmented fecal loss of thyroxine (T4), but methimazole was without effect in this respect in rats. In vitro uptake of labeled T4 by the liver was significantly enhanced by a small amount of propylthiouracil in the presence of dilute rat plasma. Methimazole was without effect under comparable conditions. In contrast, propylthiouracil and methimazole failed to affect in vitro uptake of labeled T4 by the kidney and diaphragm in the presence of dilute rat plasma. Since deiodination of T4 does not occur in the presence of dilute rat plasma, it is suggested that propylthiouracil specifically stimulates liver uptake of T4 as an initial step of an increase of biliary-fecal excretion of T4 in rats.

Effect of normalization of hypometabolic state on blood pressure in spontaneously hypertensive rats and in patients with essential hypertension

Spontaneously hypertensive rats (SHR) manifest a hypothyroid state as evidenced by increased thyroid weight, an increased level of plasma thyroid-stimulating hormone (TSH) and a decreased level of plasma thyroxine (T4) and triiodothyronine (T3). In 18 patients with essential hypertension, plasma TSH, T4 and T3 concentrations were all within the normal range, but the T4 level was significantly lower than in the controls. Among 21 hypothyroid patients, 2 had essential hypertension. Administration of thyroid hormone brought the metabolic state to normal in SHR and in hypothyroid patients but failed to affect the blood pressure. It is suggested that abnormality of thyroid function is neither the cause nor the accentuating factor in the development of hypertension in SH rats and in man.

Inhibitory effect of large doses of propylthiouracil and methimazole on an increase of thyroid radioiodine release in response to thyrotropin

Thyroidal radioiodine release increased shortly after a single injection of small doses of PTU, while moderate doses of MMI produced a similar increase of thyroidal radioiodine release with a latency of 7-9 hr. Large doses of PTU and MMI failed to augment thyroidal radioiodine release for at least 29 to 34 hr after the initial administration of goitrogens, although plasma TSH increased significantly because of goitrogen administration. An increase of thyroid hormone release in response to exogenous TSH was depressed by PTU and MMI in rats and mice treated with T4. Since this depression of TSH action only continued for a short period in spite of continuous administration of goitrogens, and since final thyroidal radioiodine release rate was similar to that produced by small doses of PTU, the effects mentioned were not simply due to general toxic action of goitrogens. It is suggested that large doses of PTU and MMI not only block thyroid hormone synthesis but also interfere with the action of TSH on thyroid hormone secretion.

Effect of butyldiiodohydroxybenzoate on pituitary-thyroid interplay

The effect of BHDB, an analogue of thyroxine, on the pituitary-thyroid system was studied in the rat. BHDB produced low plasma T4 and T3 concentrations similar to those produced by methimazole, but failed to elevate plasma TSH and to produce goiter because of displacement of T4 from the binding protein. Low plasma thyroid hormone concentrations were due to an increase of fecal loss of thyroid hormones. By releasing excess iodide, BHDB blocked the development of goiter produced by methimazole.