I. Introduction WHILE the effects of hyper- and hypothyroidism1 in female gonadal functions are well established (1, 2), controversy exists regarding the impact of thyroid diseases on male reproduction. This is due to various reasons: 1) the apparent clinical irrelevance of signs and symptoms related to male gonadal function, compared with the systemic effects of hyper- and hypothyroidism; 2) the paucity of well controlled clinical studies, due to the fact that thyroid diseases are more common in females than in males; and 3) the demonstration in the 1950s that the adult male gonad of experimental animals is metabolically unresponsive to thyroid hormone (3). Since then, the concept that the testis is unaffected by iodothyronines became widely accepted. For this reason, the potential of thyroid hormone in the modulation of male reproductive functions was not determined for several years. Indeed, in experimental studies on the effect of thyroid hormone in various tissues, the testis has been used as a negat...

Thyroid hormone and male gonadal function

Steroid and gonadotropin levels in women during the peri-menopausal years

Background: Although several studies have suggested that hormone replacement therapy lowers the risk of AD among postmenopausal women, few studies have evaluated the relationship of endogenous estrogen levels and AD. The current study investigated whether serum estrone and estradiol levels were related to the presence of AD among postmenopausal women not currently taking hormone replacement therapy. Methods: Using a case–control design, we examined an ethnically diverse sample of postmenopausal women who met National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association criteria for AD (n = 50) and nondemented controls (n = 93). All women were participants in a study of aging and dementia and were seen consecutively between August 1997 and October 1998. Results: Patients with AD had lower estradiol (F[1,141] = 8.3, p = 0.005) levels than did normal controls. Patients also had lower estrone levels; however, this comparison did not quite meet significance criteria (F[1,141] = 3.6, p = 0.06). Compared to estradiol levels >20 pg/mL, women with AD were four to six times more likely to have levels Conclusions: The results of this preliminary case–control study suggest that estradiol levels may decline significantly in women in whom AD develops.

Endogenous estrogen levels and Alzheimer’s disease among postmenopausal women

Effects of dietary fat and fiber on plasma and urine androgens and estrogens in men: a controlled feeding study.

Human breast carcinomas contain aromatase, the enzyme necessary for the conversion of androgens to estrogens. If present in sufficient amounts, aromatase could catalyze the synthesis of estrogens from plasma steroid precursors and produce high breast cancer tissue concentrations. To determine the biological importance of tumor aromatase, we validated a specific and highly sensitive 3H-labeled water release assay for aromatase and used this to quantitate the amount of estrogen synthesized in vitro in breast tumors. As proof of assay validity, the [3H]water release assay detected 22.7 ± 0.09 (±sem) pmol/g h estrogen formed vs. 24.7 pmol/g-h with the direct product isolation assay. Of 61 human breast tumors studied, 48 contained measurable aromatase activity, ranging from 5–70.5 pmol estrone formed/g·h. Three aromatase inhibitors (aminoglutethimide, testololactone, and 4-hydroxyandrostenedione) blocked this activity at concentrations similar to those affecting aromatase activity in other tissues. If biologic...

Biological Significance of Aromatase Activity in Human Breast Tumors

In order to characterize aromatization in vivo , an androgen and an estrogen, labeled with different radioactive isotopes, are administered simultaneously, either as a pulse alone or as a pulse followed by a constant infusion of the same radiolabeled steroids. Subsequently, blood samples are obtained at varying time intervals and analyzed for the 3 H/ 14 C ratio in nonmetabolized unconjugated estrogen, and/or all urine is collected for 96 hr and analyzed for the 3 H/ 14 C ratio in an estrogen conjugate. The fraction of androgen (An) entering the blood which is converted to and measured as a specific estrogen (Es) in the blood ([ρ]??) is calculated from ?? where ( 3 H-Es/ 14 C-Es) B is the ratio of radioactivities in the specific estrogen in blood; ( 3 H-An/ 14 C-Es) inj is the ratio of radioactivities administered. The fraction of androgen administered which is converted to a specific estrogen in the body and measured as a specific estrogen conjugate in the urine ([ρ]??) is calculated from ?? where ( 3 H-An/ 14 C-Es) M ) is the ratio of radioactivities in the specific estrogen conjugate. Irrespective of the method used, the aromatization of androstenedione is greater than the aromatization of testosterone; aromatization in normal men is greater than that in normal young women; aromatization in postmenopausal women is greater than that in premenopausal women. Aromatization occurs in many tissues but especially in adipose tissue and muscle, and to a lesser extent in brain, kidney, and skin. The liver appears to be a relatively minor site for aromatization in normal subjects. In certain diseases, e.g. , hepatic cirrhosis and obesity, aromatization rates are increased compared to those rates in normal individuals. In men and postmenopausal women, peripheral aromatization of androgen is a major source of circulating estrogens. The peripheral aromatization of an androgen does not appear to be influenced by luteinizing hormone, follicle-stimulating hormone or adrenocorticotropic hormone or by substrate or product concentration. Blood flow through peripheral tissues may play a major role in control of this physiologically important reaction.

https://cancerres.aacrjournals.org/content/canres/42/8_Supplement/3307s.full.pdf

Methods and Results of Aromatization Studies in Vivo

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Methods and Results of Aromatization Studies in Vivo