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Biomedical subjects

C T Sawin

Publications and source records attributed to C T Sawin.

At least 19 recordsLinked to original sources
PubMed1991

Low serum thyrotropin (thyroid-stimulating hormone) in older persons without hyperthyroidism.

We studied a large population (n = 2575) of unselected ambulatory persons older than 60 years to determine the prevalence of a low serum thyroid-stimulating hormone (TSH) level, ie, of less than 0.1 mU/L using a sensitive assay, a level suggestive of hyperthyroidism in younger adults. One hundred one persons (3.9%) had a low serum TSH level. About half of them (51/101) were taking thyroid hormone. Of the remainder, 44 were not hyperthyroid did not become so during up to 4 years of follow-up. Forty-one of the 44 euthyroid persons had a serum thyroxine level of less than 129 nmol/L; repeated testing showed a serum TSH level of more than 0.1 mU/L in the three euthyroid persons with a serum thyroxine level of more than 129 nmol/L. Only six were hyperthyroid or became so during the follow-up period; all had a serum thyroxine level of more than 129 nmol/L. Routine clinical examination was not a sensitive indicator of hyperthyroidism and did not permit discrimination from euthyroidism. A low value of serum TSH alone, while it had high sensitivity and specificity for hyperthyroidism, had a low positive predictive value (12%) for this diagnosis; addition of the thyroxine assay raised the predictive value fivefold to 67%. A low value of serum TSH is far more common in older persons than is hyperthyroidism. Low values in euthyroid persons are accompanied by a clearly normal serum T4 concentration (less than 129 nmol/L) or by a serum TSH level of more than 0.1 mU/L on repeated testing. We recommend measurement of the serum TSH thyroid concentration, using a sensitive assay, as the initial step in testing any older person for possible hyperthyroidism. Measurement of the serum T4 concentration or the free T4 index on the same sample would be needed only in the approximately 2% with a serum TSH level of less than 0.1 mU/L; alternatively, the TSH assay in these could be repeated at a later time.

Aged↗
PubMed1989

The aging thyroid. The use of thyroid hormone in older persons.

The overall prevalence of thyroid hormone use in an unselected population of older adults (n = 2575; average age, 68.6 years) was 6.9% (10.0% in women and 2.3% in men). Eighty-one percent of women taking it were doing so for appropriate indications, eg, hypothyroidism, while 12% were not, eg, for obesity or high serum cholesterol; more men (29%) were taking it inappropriately. Inappropriate use was associated with desiccated thyroid more than with thyroxine. After follow-up averaging 6.9 years, 58% of inappropriate users were still taking it. Underuse also occurred. Thirty-seven percent of those definitely hypothyroid had a clearly elevated serum thyrotropin level (greater than 10 mU/L) despite thyroid therapy. Thyroid therapy is common in the elderly; most is appropriate. When inappropriate use occurs, it is more common in men and more often associated with desiccated thyroid, still commonly used in this age group. In chronic users of thyroid hormone, it is important to review currently appropriate indications and to measure serum thyrotropin levels to assess the adequacy of treatment of primary hypothyroidism.

Age Factors↗
PubMed1989

Serum prolactin and aging: basal values and changes with estrogen use and hypothyroidism.

We studied basal serum prolactin in older (greater than age 50) men (N = 501) and women (N = 384) using younger adults for comparison and excluding those taking medications. Serum prolactin rose slightly with increasing age in men; it fell slightly in women until age 80, when it rose slightly. Men and women were not different except for the higher value in women at age 20 to 29. Serum prolactin did not fall after the menopause, while estrogen treatment had no effect on older women and caused only a slight rise in older men. Thyroid deficiency had only a minimal effect and did not raise the serum prolactin above 25 ng/ml. The prevalence of clearly elevated values (greater than 20 ng/ml) was only 1.3% in women and 0.6% in men above age 50; there is little evidence for a significant prevalence of prolactin-secreting adenomata in older persons. In older persons, prolactin-secreting tumors are uncommon, and neither thyroid failure nor estrogen therapy are good explanations for a clearly elevated serum prolactin.

Adult↗
PubMed1989

'Natural' desiccated thyroid. A 'health-food' thyroid preparation.

"Natural" thyroid preparations, a type of bovine desiccated thyroid, are sold without prescription in "health-food" stores or by mail; they may or may not contain thyroid hormone. One such preparation was the cause of erratic thyroid test results in a patient who took it instead of thyroxine. Further study showed that the preparation contained biologically active thyroid hormone and was capable of causing hyperthyroidism. Natural thyroid preparations are biologically active yet unstandardized; because the hormonal content of a natural thyroid product is unknown, its use as a substitute for thyroxine can lead either to relapse of hypothyroidism or to hyperthyroidism.

Adult↗
PubMed1979

The aging thyroid. Increased prevalence of elevated serum thyrotropin levels in the elderly.

Of 344 relatively healthy persons older than 60 years, 22 (5.9%) had a clearly elevated level of serum thyrotropin (TSH) (greater than 10 muU/mL), a finding more common in women than in men. Ten of the 22 had low values for serum thyroxine (T4) and free T4 (FT4) index, but only one had a low value for serum triiodothyronine (T3) or free T3 (FT3) index. A further 14.4% had a slightly elevated level of serum TSH (greater than 5 less than or equal to 10 muU/mL), but none had low values for serum T4 or FT4 index. Age alone has little effect on the measurements of T4; age is associated with slightly lower T3 levels, but only in men 60 years or older or in women 80 years or older. Longitudinal studies should determine if a slightly elevated serum TSH rises further with age and if there is a causal relationship between a high level of serum TSH and cardiovascular disease.

Aged↗
PubMed1979

Relationship of iodide-induced increase in TSH response to TRH to changes in serum thyroid hormones.

Large doses of iodide (500 mg three times a day) administered to normal men for 10--12 days caused a rise in basal serum TSH and a concomitant rise in the peak TSH response to TRH. The basal and peak levels of TSH were highly correlated (p less than 0.001). However, the iodide-induced rise in the peak TSH after TRH was poorly correlated with concomitant changes in serum thyroid hormones. Serum T3 wa not lower after iodide and, while serum T4 was somewhat lower, the fall in serum T4 was unexpectedly inversely rather than directly correlated with the rise in the peak TSH response to TRH. Thus, increased TSH secretion after iodide need not always be directly correlated with decreased concentrations of circulating thyroid hormones even when large doses of iodide are used. Clinically, a patient taking iodide may have an increased TSH response in a TRH stimulation test even though there is little or no change in the serum level of T3 or T4.

Adolescent↗
PubMed1978

Transient suppression of growth hormone secretion after chronic ethanol intake.

Fifty-two percent of patients with chronic heavy intake of ethanol had an abnormally low growth hormone (GH) response to propranolo-glucagon. The effect of ethanol is transient, since the GH response was normal in patients studied 2 wk or more after withdrawal of ethanol. The low GH response was not due to a difference in the levels of glucose or insulin. Ethanol probably suppresses the GH response by acting on the hypothalamus or pituitary gland. Along with previous data suggesting transient ACTH deficiency in chronic alcoholic patients, our findings suggest that these patients may have multiple hypothalamic-pituitary deficiencies.

Adult↗
PubMed1978

Riedel's struma associated with subacute thyroiditis, hypothyroidism, and hypoparathyroidism.

Riedel's struma with dense fibrous invasion of surrounding muscle and fat was found in a patient who had clinical subacute thyroiditis superimposed on primary hypothyroidism. Riedel's struma may sometimes be an uncommon stage in the more common subacute form of thyroiditis, although in our patient an unusual coincidence of subacute thyroiditis and Riedel's struma is also possible. Of interest in our patient was the development of spontaneous primary hypoparathyroidism; parathyroid function returned to normal concomitant with the spontaneous resolution of the goiter after partial resection. This patient also represents another instance of hyperthyroidism developing in a previously hypothyroid patient.

Female↗
PubMed1978

Effect of chronic administration of estrogen, androgen, or both on serum levels of gonadotropins in adult men.

Ethinyl estradiol (50 micrograms/day) or fluoxymesterone (10 or 20 mg/day), chosen because each is orally active and because fluoxymesterone is probably not converted to an estrogen, were given alone and in combination to adult men over several weeks. Measurements were made of serum FSH, LH, testosterone, and estradiol. The estrogen given alone suppressed serum FSH while the androgen given alone did not; however, the androgen may have enhanced the suppressive effect of the estrogen on the serum FSH. Neither steroid alone changed the serum LH but both together suppressed it. The estrogen alone decreased the serum testosterone, an effect probably mediated by the concomitant fall in serum FSH and a resulting decrease in sensitivity to the constant level of LH; a direct effect of estrogen on the testis seems less likely. The doses of estrogen and androgen used probably had a biologic effect equal to or somewhat above that of endogenously produced estrogen and androgen and thus reflected the maximum physiological effects of the endogenous steroids. Thus, in the chronic physiological control of FSH and LH in adult men, these data indicate that (1) testosterone alone, as an androgen, has little effect on FSH or LH, (2) estradiol (or total estrogen) has a greater suppressive effect on FSH than on LH and by its effect on FSH may indirectly regulate the secretion of testosterone, and (3) testosterone and estradiol together may be involved in the regulation of both FSH and LH.

Adult↗
PubMed1978

Effect of thyroid hormones on the prolactin response to thyrotropin-releasing hormone in normal persons and euthyroid goitrous patients.

In nine euthyroid goitrous patients, increasing doses of T4 caused a significant decrease in the PRL response to TRH; the PRL response fell significantly at a dose of T4 of 100 micrograms/day for 1 month (P less than 0.02) and fell further with increasing doses so that at 300 micrograms T4/day, the PRL response was 40% of that in the untreated state. T4 treatment also blunted the PRL response to chlorpromazine (P less than 0.05) in a separate group of euthyroid goitrous patients. In contrast, there was only a small drop of the PRL response to TRH in normal subjects treated with T4 (n = 9) and none at all with T3 (n = 7). These data, together with previously published reports, suggest that thyroid hormone may affect PRL secretion in the presence of thyroid disease (hyperthyroidism, hypothyroidism, or euthyroid goiter), but that physiological amounts of thyroid hormone have little or no modulating effect on PRL secretion in normal persons.

Adolescent↗
PubMed1978

The relationship of changes in serum estradiol and progesterone during the menstrual cycle to the thyrotropin and prolactin responses to thyrotropin-releasing hormone.

The responses of serum TSH and PRL to TRH (500 microgram) were studied in normal young women in the early follicular, periovulatory, and midluteal phases of the menstrual cycle in order to examine the relationship of these responses to the levels of estradiol relationship of these responses to the levels of estradiol (E2) and progesterone. Each woman was studied twice in each phase in order to assess intraindividual variability. There was no significant difference in either the TSH or PRL responses among the phases of the menstrual cycle nor was either response affected by the periovulatory rise in E2 or by the luteal rise in both E2 and progesterone. Thus, the interpretation of the TSH and PRL responses to TRH in normal women is not affected by the menstrual cycle although both responses are greater in women that in men. Both the peak TSH and peak PRL after TRH were highly correlated with the basal levels of TSH (r = 0.85; P less than 0.01) and PRL (r = 0.67; P less than 0.01), respectively, indicating that the TSH and PRL responses to TRH in women are directly proportionate to the basal levels of the respective hormones, as previously shown for the TSH response in men. The mean intraindividual variability (coefficient of variation) of the TSH response to TRH was 18%, but ranged as high as 56%, while that of the PRL response was 16% and ranged up to 31%; variability was not affected by the phase of the menstrual cycle. The normal range of the peak TSH after TRH in women is 7-33 microU/ml (mean +/- 2 SD); however, because of the variability, a normal woman may sometimes have a peak TSH after TRH as low as 4 microU/ml. Repeating the test will result in a normal value if the woman is truly normal. Similarly, the normal peak PRL after TRH in women is 22-111 ng/ml (mean +/- 2 SD); usually, however, the lower limit is 30 ng/ml with lower values due to intraindividual variation. The data suggest that the higher average level of E2 in women compared to women, but that the cyclic changes in serum E2 or progesterone in women have little or no additional effect.

Adult↗
PubMed1978

The free triiodothyronine (T3) index.

In a large number of normal men (n = 111) and women (n = 110) the free triiodothyronine (T3), index, calculated from serum total T3 and T3-uptake, was highly correlated with free T3, measured by equilibrium dialysis. The correlation was almost as high as that of the free thyroxine (T4) index with free T4. The correlations of the total T3, free T3, and free T3 index with, respectively, the total T4, free T4, and free T4 index were much lower, though still statistically significant. The free T3 index is clinically useful because serum total T3 may sometimes be misleading. Hyperthyroid patients with apparent T4-toxicosis and normal total T3 may have an elevated free T3 index and thus physiologically elevated levels of both thyroid hormones. Calculation of the free T3 index might also make possible the diagnosis of T3-toxicosis in a patient with a normal free T4 index and normal total T3. Total T3 may be elevated without an elevated total T4 in women taking oral contraceptives; thus the free T3 index may prevent a misdiagnosis of T3-toxicosis. The free T3 index seems no better than total T3 in the diagnosis of primary hypothyroidism, but it can confirm the diagnosis of T3-hypothyroidism.

Adult↗