Thyroid hormone, glucocorticoids, and prolactin at the nexus of physiology, reproduction, and toxicology

Cooke, Paul S.; Holsberger, Denise R.; Witorsch, Raphael J.; Sylvester, Paul W.; Meredith, John M.; Treinen, Kimberley A.; Chapin, Robert E.

doi:10.1016/j.taap.2003.09.016

Cited by 80 publications

(50 citation statements)

References 167 publications

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“…Prolactin is a peptide hormone cytokine with a wide range of biological activities outside of its well-known role in lactation (Grattan and Kokay 2008). For an excellent and concise high-level summary, see the PRL section in Cooke et al (2004).…”

Section: Prolactinmentioning

confidence: 99%

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Assessment of Circulating Hormones in Regulatory Toxicity Studies II. Male Reproductive Hormones

Chapin

Creasy²

2012

Toxicol Pathol

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When test article-related testicular toxicity or Leydig cell tumors are identified in nonclinical studies, the measurement of circulating hormones such as luteinizing hormone, follicle-stimulating hormone, inhibin, testosterone, or prolactin is often considered in order to aid mechanistic investigations or to identify potential biomarkers in man. Although some hormone levels are relatively constant, others are subject to wide variability owing to pulsatility of secretion, diurnal rhythms, and stress. To avoid being misled, it is important that this variation is factored into any study design that includes hormone measurements. Since all these possibilities start from the pathologist's reading of the tissue sections, we begin with a review of the morphologic changes that are tied to underlying alterations in hormones. We then provide the reader with basic information and representative hormone data, including coefficients of variation, for the major male reproductive hormones in the three main nonclinical species (rats, dogs, and cynomolgus monkeys). Power and probability tables for rats and dogs allow estimates of the number of animals or samples needed to provide a given likelihood of detecting a hormonal change of a given size. More importantly, we highlight the variability of this process and the real value in readers developing this information at their own site.

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Section: Prolactinmentioning

confidence: 99%

“…It is well understood that PRL release in human males follows a circadian rhythm, characterized by increased secretion during hours of sleep (Cooke et al 2004). However, this secretion pattern has not been clearly demonstrated in male rats.…”

Section: Prolactinmentioning

confidence: 99%

Assessment of Circulating Hormones in Regulatory Toxicity Studies II. Male Reproductive Hormones

Chapin

Creasy²

2012

Toxicol Pathol

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“…Steroid hormones play a critical role in the male reproductive function (for review, see Michael et al, 2003;Cooke et al, 2004;Patrão et al, 2009;Verhoeven et al, 2010). Disturbances in their metabolism and signalling are known to impair both spermatogenesis and epididymal sperm maturation, causing a negative impact in fertility.…”

Section: Introductionmentioning

confidence: 99%

“…Disturbances in their metabolism and signalling are known to impair both spermatogenesis and epididymal sperm maturation, causing a negative impact in fertility. Glucocorticoids are a class of adrenal steroid hormones known to have complex roles in the male reproductive tract (Cooke et al, 2004). For example, it is well established that conditions associated with high levels of circulating glucocorticoids, as observed in stress, Cushing syndrome, and long-term therapy with synthetic glucocorticoids, disrupt male fertility (Gabrilove et al, 1974;Sapolsky, 1985;Cooke et al, 2004;Hardy et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

“…Glucocorticoids are a class of adrenal steroid hormones known to have complex roles in the male reproductive tract (Cooke et al, 2004). For example, it is well established that conditions associated with high levels of circulating glucocorticoids, as observed in stress, Cushing syndrome, and long-term therapy with synthetic glucocorticoids, disrupt male fertility (Gabrilove et al, 1974;Sapolsky, 1985;Cooke et al, 2004;Hardy et al, 2005). High plasma levels of glucocorticoids induce reproductive dysfunction by multiple mechanisms, such as suppression of testicular response to gonadotropins (Welsh et al, 1982;Sapolsky, 1985;Orr & Mann, 1992), down-regulation of genes encoding testosterone biosynthetic enzymes (Hales & Payne, 1989;Payne & Sha, 1991;Badrinarayanan et al, 2006), induction of Leydig cell and germ cell apoptosis (Yazawa et al, 2000;Gao et al, 2002Gao et al, , 2003, and induction of oxidative stress in the epididymis (Balasubramanian et al, 1987;Dhanabalan et al, 2010Dhanabalan et al, , 2011Dhanabalan et al, , 2013.…”

Section: Introductionmentioning

confidence: 99%

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Impact of adrenalectomy and dexamethasone treatment on testicular morphology and sperm parameters in rats: insights into the adrenal control of male reproduction

et al. 2014

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SUMMARYHere we investigated the hypothesis that normal levels of glucocorticoids, a class of adrenal steroid hormones, are required for normal testicular and epididymal functions. We examined the effects of the manipulation of glucocorticoid plasma levels by bilateral adrenalectomy (1, 2, 7 and 15 days) alone or in combination with daily treatment with the synthetic glucocorticoid dexamethasone (DEX; 5 lg/kg, i.p., 6 days) on the morphology of the testis and sperm parameters in rats. We showed that adrenalectomy led to a reduction in testicular sperm count and daily sperm production starting 2 days after surgery and a differential decrease in sperm count in the epididymis, according to the region and time post-adrenalectomy analysed. In parallel, testes from 7-day adrenalectomized (ADX) rats displayed a higher frequency of damaged seminiferous tubules and the presence of elongated spermatids retained in the basal epithelial compartment in stages IX-XVII, which is indicative of defective spermiation. The alkaline comet assay revealed a late effect of adrenalectomy on epididymal sperm DNA fragmentation, which was increased only 15 days after surgery. DEX treatment prevented the changes in testicular and epididymal sperm count observed in 7-day ADX rats, but failed to protect the testis from ADX-induced morphological abnormalities. Thus, our results indicated that glucocorticoids may be involved in events related to the maintenance of spermatogenesis and sperm maturation during adulthood. These findings provide new insights into the importance of adrenal steroids to male fertility.

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Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields

Burchard

Nguyen

Rodríguez

2006

Bioelectromagnetics

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Two experiments were carried out to assess the effects of electric and magnetic fields (EMF) on blood thyroxine (T4) in dairy cattle. In experiment 1, 16 lactating pregnant Holstein cows were exposed to 10 kV/m, 30 microTesla (microT) EMF. The animals were divided into two groups of eight animals each. Each group was exposed to EMF according to one of two treatment sequences of three periods of 28 days each. Sequence 1 was EMF OFF-ON-OFF and sequence 2 was EMF ON-OFF-ON. During the last day of each treatment period, blood samples were collected every 4 h for 24 h to estimate T4 plasma concentrations. In experiment 2, 16 nonlactating, nonpregnant, multiparous Holsteins were exposed to 10 kV/m, 30 microT EMF. The animals were divided into two groups of eight animals each. Each group was exposed to EMF according to one of the two treatment sequences described above, except that each period amounted to the number of days corresponding to one estrous cycle. During treatment, blood samples were collected every other day for T4 analysis. In both experiments, the light cycle emulated a short photoperiod (8 h light/16 h dark). During the ON periods, the animals were exposed to EMF for 16 h, 8 h of the light period plus the first 8 h of during the dark period. In experiment 1, exposed animals did not have any change in T4 plasma concentrations due to treatment (P = .0968), but, the time of sample collection revealed a significant difference (P = .0012). In experiment 2, the effect of period (P = .0009) and the treatment by days interaction (P = .0003) were statistically significant. We conclude that a worst case scenario exposure of dairy cattle to 10 kV/m, 30 microT EMF influences, in a moderate fashion, the blood levels of thyroxine.

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Thyroid hormone, glucocorticoids, and prolactin at the nexus of physiology, reproduction, and toxicology

Cited by 80 publications

References 167 publications

Assessment of Circulating Hormones in Regulatory Toxicity Studies II. Male Reproductive Hormones

Assessment of Circulating Hormones in Regulatory Toxicity Studies II. Male Reproductive Hormones

Impact of adrenalectomy and dexamethasone treatment on testicular morphology and sperm parameters in rats: insights into the adrenal control of male reproduction

Plasma concentrations of thyroxine in dairy cows exposed to 60 Hz electric and magnetic fields

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