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Nathan Goodyear

Aromatase Inhibition in the Human Male Reveals a Hypothalamic Site of Estrogen Feedback - 0 views

jcem.endojournals.org/...3027.long

estrogen estradiol estrone testosterone low T HPA hypothalamus pituitary male

shared by Nathan Goodyear on 25 Apr 12 - No Cached
  • Nathan Goodyear on 25 Apr 12
     
    estrogen shown to have two sites of negative feedback in men. First in the hypothalamus and second in the pituitary.  In many men, aromatase inhibition can restore the HPA by eliminating the negative feedback of estrogen on the hypothalamus and the pituitary.
Nathan Goodyear

Aromatase Inhibition in the Human Male Reveals a Hypothalamic Site of Estrogen Feedback - 0 views

jcem.endojournals.org/...3027.short

estrogen hypothalamus pituitary aromatase inhibition inhibitor men male negative feedback

shared by Nathan Goodyear on 12 Feb 12 - No Cached
  • Nathan Goodyear on 12 Feb 12
     
    estrogen shown to inhibit testosterone production at both the hypothalamus and pituitary through negative feedback.
Nathan Goodyear

Cortisol inhibition of vasopressin and ACTH res... [Am J Physiol. 1990] - PubMed - NCBI - 0 views

www.ncbi.nlm.nih.gov/...2154137

cortisol ACTH vasopressin hormone hormones

shared by Nathan Goodyear on 06 Aug 13 - No Cached
  • Nathan Goodyear on 06 Aug 13
     
    negative feedback of cortisol on pituitary ACTH and vasopressin release.  Animal study, but shows the central feedback of cortisol on the pituitary.
Nathan Goodyear

Differential Regulation of Gonadotropin Secretion by Testosterone in the Human Male: Ab... - 0 views

jcem.endojournals.org/...53.long

Testosterone men T E2 estradiol FSH LH HPA male hormone regulation

shared by Nathan Goodyear on 25 Apr 12 - No Cached
  • Nathan Goodyear on 25 Apr 12
     
    In men, Testosterone is shown to provide negative feedback on LH; but FSH is primarily regulated by estradiol.
Nathan Goodyear

Aromatase Inhibition in the Human Male Reveals a Hypothalamic Site of Estrogen Feedback - 0 views

jcem.endojournals.org/...3027.full

anastrozole arimidex aromatase inhibition men E2 estradiol Testosterone low T hypothalamus pituitary

shared by Nathan Goodyear on 15 Mar 12 - No Cached
  • Nathan Goodyear on 15 Mar 12
     
    aromatase inhiibition via anastrozole decreased Estradiol and allowed for an increase in Testosterone production.  Estradiol has a negative feedback at both the hypothalamus and the pituitary.
Nathan Goodyear

Estradiol, but not testosterone, heightens cortisol-mediated negative feedback on pulsa... - 0 views

ajpregu.physiology.org/...R627

Testosterone Estradiol hormone hormones cortisol ACTH stress

shared by Nathan Goodyear on 04 Apr 15 - No Cached
  • Nathan Goodyear on 04 Apr 15
     
    INteresting.  Estradiol enhances cortisol negative feedback on ACTH production in both men and women.
Nathan Goodyear

The endocrinology of sexual arousal - 0 views

joe.endocrinology-journals.org/...411.long

libido testosterone ED men women sexual arousal orgasm hormone hormones

shared by Nathan Goodyear on 08 Jun 13 - No Cached
  • A number of age-related changes may be relevant: altered negative feedback of testosterone and hence less increase in luteinizing hormone (LH) with falling testosterone levels, increased sex hormone binding globulin (SHBG) and hence relatively reduced free testosterone and the likelihood of an age-related decline in testosterone receptor sensitivity
  • In the older male, the picture is complicated by various aging effects, including altered hypothalamo–pituitary feedback, increased testosterone binding and reduced receptor sensitivity
  • The neurophysiological basis of NPT is still disputed, but one plausible explanation is that REM sleep is associated with a ‘switching off’ of the noradrenergic cells in the locus coeruleus
  • ...1 more annotation...
  • the impact of testosterone on the emergence of sexual arousability is less clear
  • Nathan Goodyear on 08 Jun 13
     
    Good discussion of the arousal/sexual response differences between men and women from a physiological perspective.  
Nathan Goodyear

Minireview: Inflammation and Obesity Pathogenesis: The Hypothalamus Heats Up - 0 views

endo.endojournals.org/...4109.full

inflammation obesity overweight hypothalamus HPA

shared by Nathan Goodyear on 04 Oct 12 - No Cached
  • Leptin, secreted by adipocytes in proportion to body fat mass
  • The saturated fatty acid palmitate (16:0) induces NF-κB signaling through a TLR4-dependent mechanism
  • 18:0 (stearic) and longer saturated fatty acids as well as linolenic acid (18:3) increased proinflammatory cytokines, ER stress markers, and TLR4 activation
  • ...6 more annotations...
  • (SOCS)-3. A member of a protein family originally characterized as negative feedback regulators of inflammation (13, 37), SOCS3 inhibits insulin and leptin signaling
  • IKKβ signaling in discrete neuronal subsets appears to be required for both hypothalamic inflammation and excess weight gain to occur during HF feeding
  • the paradoxical observation that hyperphagia and weight gain occur when hypothalamic inflammation is induced by HF feeding, yet when it occurs in response to systemic or local inflammatory processes (e.g. administration of endotoxin), anorexia and weight loss are the rule
  • , serves as a circulating signal of energy stores in part by providing feedback inhibition of hypothalamic orexigenic pathways [e.g. neurons that express neuropeptide Y and agouti-related peptide (AgRP)]
  • and stimulating anorexigenic neurons
  • signals from Toll-like receptors (TLRs), evolutionarily conserved pattern recognition molecules critical for detecting pathogens, amplified through signaling intermediates such as MyD88 activate the inhibitor of κB-kinase-β (IKKβ)/nuclear factor-κB (NF-κB), c-Jun N-terminal kinase (Jnk) and other intracellular inflammatory signals in response to stimulation by circulating saturated fatty acids
  • Nathan Goodyear on 04 Oct 12
     
    great read on the current understanding of how obesity and resultant inflammation disrupts hypothalamic function.
Nathan Goodyear

Decreased androgen levels and obesity in men. [Ann Med. 1996] - PubMed - NCBI - 0 views

www.ncbi.nlm.nih.gov/...8932500

obesity low T testosterone hypogonadotrophic hypogonadism estrogen aromatase LH

shared by Nathan Goodyear on 11 Feb 12 - No Cached
  • Nathan Goodyear on 11 Feb 12
     
    As obesity increases, so Testosterone decreases.  Hypogondatrophic hypogonadism is associated is found in obesity.  This is no surprise, as aromatase activity is increased in fat resulting in elevated Estrogen, which provides negative feedback to the hypothalamic-pituitary axis.  This results in decrease LH and thus Testosterone production.
Nathan Goodyear

Dihydrotestosterone may inhibit hypothalamo-pi... [Neurosci Lett. 2004] - PubMed - NCBI - 0 views

www.ncbi.nlm.nih.gov/...15234470

hormone hormones DHT metabolite metabolites 3-beta androstanediol 3-beta-diol ER estrogen receptor ER beta ER-beta

shared by Nathan Goodyear on 03 Feb 14 - No Cached
  • Nathan Goodyear on 03 Feb 14
     
    Mouse study finds that DHT metabolite provides negative feedback to HPA via 3beta androstaendiol.  What is interesting is that this signaling occurred through ER beta.  Androgen signaling processed through estrogen receptors.
Nathan Goodyear

Intermediary metabolism of fructose. - 0 views

ajcn.nutrition.org/...754S.full.pdf+html

fructose metabolism

shared by Nathan Goodyear on 19 Sep 13 - No Cached
  • Nathan Goodyear on 19 Sep 13
     
    Good review on the metabolism of fructose.  Fructose is able to bypass the key regulatory step in glycolysis and promote Triglyceride synthesis without any negative feedback.
Nathan Goodyear

Salivary Testosterone and a Trinucleotide (CAG) Length Polymorphism in the Androgen Rec... - 0 views

www.ncbi.nlm.nih.gov/...PMC2825741

CAG androgen receptors AR androgen receptor Testosterone hormone hormones male men

shared by Nathan Goodyear on 22 Jun 15 - No Cached
  • Testosterone correlated inversely with participant age (r = −0.39, p = 0.012) and positively with number of CAG repeats
  • transactivation potential of the AR appears to decline in graded relation to an increasing number of CAG repeats, which are distributed over a normative range of 11–37 and, in Caucasian populations, commonly average 21–22 repeats
  • When activated by androgens, ARs translocate to the cell nucleus, where they exert transcriptional control of androgen-dependent genes by binding to androgen response elements within gene regulatory sequences
  • ...10 more annotations...
  • some evidence suggests a high number of CAG repeats may be associated with cognitive aging
  • androgens (like other steroid hormones) promote or repress the expression of genes specifying an array of cellular proteins
  • diurnal variation in testosterone levels
  • salivary testosterone correlated negatively with participant age and positively with CAG length variation in the AR gene
  • CAG repeat number varied inversely with reactivity of the ventral amygdala to facial expressions of negative affect
  • higher salivary testosterone was likewise associated with a greater number of AR CAG repeats
  • relative androgen insensitivity in ARs with a larger number of CAG repeats
  • Because circulating testosterone is regulated via negative feedback through the hypothalamic-pituitary-gonadal axis, diminished androgen sensitivity at higher CAG repeat lengths may reduce feedback suppression of luteinizing hormone (LH). LH would then be maintained at higher levels, in turn promoting higher testosterone production
  • Testosterone up-regulates AVP expression in the amygdala
  • Oxytocin exerts an inhibitory influence on AVP expression in the central amygdala, and the synthesis of oxytocin is mediated by estrogen and estrogen receptors
  • Nathan Goodyear on 22 Jun 15
     
    Study used saliva to measure Testosterone levels in men.  Testosterone levels were inversely associated with age, but positively associated with CAG repeat sequences in the AR.
Nathan Goodyear

Short-Term Aromatase-Enzyme Blockade Unmasks Impaired Feedback Adaptations in Luteinizi... - 0 views

jcem.endojournals.org/...211

low Testosterone estrogen LH

shared by Nathan Goodyear on 14 Jan 11 - No Cached
  • administration of a potent and selective aromatase antagonist reduces estradiol and elevates mean LH concentrations equivalently in young and older men. The low estrogen-feedback state in elderly men unmasks diminished incremental LH pulse amplitude and area; absence of further acceleration of LH pulse frequency; impaired regulation of the orderliness of LH release; and reduced testosterone to SHBG ratios
  • Nathan Goodyear on 14 Jan 11
     
    estrogen decreases testosterone production
Nathan Goodyear

Clomiphene citrate effects on testosterone/estroge... [J Sex Med. 2005] - PubMed - NCBI - 0 views

www.ncbi.nlm.nih.gov/...16422830

clomid HPA low T testosterone estrogen estradiol hypogonadism men male hormone hormones

shared by Nathan Goodyear on 24 Jul 14 - No Cached
  • Nathan Goodyear on 24 Jul 14
     
    small cohort with low serum Total Testosterone improved T:E2 ratio with clomid.  Clomid restores the HPA through inhibition of the negative feedback of Estradiol on the Hypothalamus and Pituitary in men.  This allows for an increase in gonadotropin production and thus increase in testosterone production.  Aromatase inhibition therapy would likely still prove beneficial in this situation.
Nathan Goodyear

Histidine suppresses food intake through its conversion into neuronal histamine. - PubM... - 0 views

www.ncbi.nlm.nih.gov/...11788786

histidine histamine leptin metabolism

shared by Nathan Goodyear on 13 Jan 16 - No Cached
  • Nathan Goodyear on 13 Jan 16
     
    neuronal histidine to histamine conversion suppresses appetite via leptin feedback signaling.  
Nathan Goodyear

Sex hormone synthesis, regulation, and function | McMaster Pathophysiology Review - 0 views

www.pathophys.org/sexhormones

hormones HPA Testosterone DHEA estradiol LH FSH Progesterone androgens estrogen

shared by Nathan Goodyear on 02 Oct 17 - No Cached
  • Nathan Goodyear on 02 Oct 17
     
    Good review of the HPA-sex hormone pathways, called the Hypothalamic-Pituitary-Gondal axis, including HP feedback.  This is not a study but has nice diagrams. This is based on 14 referenced articles and 1 book chapter.
Nathan Goodyear

Modulators of estrogen receptor inhibit prostate cancer - 0 views

www.sciencedirect.com/...S1043661813001709

curcumin hormones ER-beta prostate cancer

shared by Nathan Goodyear on 14 May 21 - No Cached
  • Nathan Goodyear on 14 May 21
     
    Curcumin inhibits prostate cancer growth through signaling with ER-beta receptor. This mimics the 3beta-androstanediol negative feedback loop.
Nathan Goodyear

The Aging Male Hypothalamic-Pituitary-Gonadal Axis: pulsatility and feedback - 0 views

www.ncbi.nlm.nih.gov/...PMC2662347

Testosterone male hormones aging male hypothalamus pituitary

shared by Nathan Goodyear on 22 Feb 17 - No Cached
  • Nathan Goodyear on 22 Feb 17
     
    good review of the male hypothalamic-pituitary-gonadal axis.  Of interest is a good discussion of the pulsatile LH activity.
Nathan Goodyear

Low early morning plasma cortisol in posttraumatic stress disorder is associated with c... - 0 views

www.sciencedirect.com/...S0306453009002509

PTSD low cortisol stress disorder depression

shared by Nathan Goodyear on 03 Feb 12 - No Cached
  • Nathan Goodyear on 03 Feb 12
     
    Low cortisol found in those with PTSD.  This study suggest the high ACTH/cortisol ratio is not due to enhanced peripheral sensitization to glucocorticoids.
Nathan Goodyear

Lowered testosterone in male obesity: Mechanisms, morbidity and management Tang Fui MN,... - 0 views

www.ajandrology.com/article.asp

Testosterone male obesity overweight men hormone hormones low T Low T

shared by Nathan Goodyear on 15 Jan 14 - No Cached
  • The number of overweight people is expected to increase from 937 million in 2005 to 1.35 billion in 2030
  • Similarly the number of obese people is projected to increase from 396 million in 2005 to 573 million in 2030
  • By 2030, China alone is predicted to have more overweight men and women than the traditional market economies combined
  • ...37 more annotations...
  • diacylglycerol O-acyltransferase 2 (DGAT2), mechanistically implicated in this differential storage, [10] is regulated by dihydrotestosterone, [11] suggesting a potential role for androgens to influence the genetic predisposition to either the MHO or MONW phenotype.
  • bariatric surgery achieves 10%-30% long-term weight loss in controlled studies
  • The fact that obese men have lower testosterone compared to lean men has been recognized for more than 30 years
  • Reductions in testosterone levels correlate with the severity of obesity and men
  • epidemiological data suggest that the single most powerful predictor of low testosterone is obesity, and that obesity is a major contributor of the age-associated decline in testosterone levels.
  • healthy ageing by itself is uncommonly associated with marked reductions in testosterone levels
  • obesity blunts this LH rise, obesity leads to hypothalamic-pituitary suppression irrespective of age which cannot be compensated for by physiological mechanisms
  • Reductions in total testosterone levels are largely a consequence of reductions in sex hormone binding globulin (SHBG) due to obesity-associated hyperinsulinemia
  • although controversial, measurement of free testosterone levels may provide a more accurate assessment of androgen status than the (usually preferred) measurement of total testosterone in situations where SHBG levels are outside the reference range
  • SHBG increases with age
  • marked obesity however is associated with an unequivocal reduction of free testosterone levels, where LH and follicle stimulating hormone (FSH) levels are usually low or inappropriately normal, suggesting that the dominant suppression occurs at the hypothalamic-pituitary level
  • adipose tissue, especially when in the inflamed, insulin-resistant state, expresses aromatase which converts testosterone to estradiol (E 2 ). Adipose E 2 in turn may feedback negatively to decrease pituitary gonadotropin secretion
  • diabetic obesity is associated with decreases in circulatory E 2
  • In addition to E 2 , increased visceral fat also releases increased amounts of pro-inflammatory cytokines, insulin and leptin; all of which may inhibit the activity of the HPT axis at multiple levels
  • In the prospective Massachusetts Male Aging Study (MMAS), moving from a non-obese to an obese state resulted in a decline of testosterone levels
  • weight loss, whether by diet or surgery, increases testosterone levels proportional to the amount of weight lost
  • fat is androgen-responsive
  • low testosterone may augment the effects of a hypercaloric diet
  • In human male ex vivo adipose tissue, testosterone decreased adipocyte differentiation by 50%.
  • Testosterone enhances catecholamine-induced lipolysis in vitro and reduces lipoprotein lipase activity and triglyceride uptake in human abdominal adipose tissue in vivo
  • in men with prostate cancer receiving 12 months of androgen deprivation therapy, fat mass increased by 3.4 kg and abdominal VAT by 22%, with the majority of these changes established within 6 months
  • severe sex steroid deficiency can increase fat mass rapidly
  • bidirectional relationship between testosterone and obesity
  • increasing body fat suppresses the HPT axis by multiple mechanisms [30] via increased secretion of pro-inflammatory cytokines, insulin resistance and diabetes; [19],[44] while on the other hand low testosterone promotes further accumulation of total and visceral fat mass, thereby exacerbating the gonadotropin inhibition
  • androgens may play a more significant role in VAT than SAT
  • men undergoing androgen depletion for prostate cancer show more marked increases in visceral compared to subcutaneous fat following treatment
    • Nathan Goodyear
      Nathan Goodyear on 16 Jan 14
       
      Interesting: low T increases VAT, yet T therapy does not reduce VAT, yet T therapy reduces SAT.
  • irisin, derived from muscle, induces brown fat-like properties in rodent white fat
  • androgens can act via the PPARg-pathway [37] which is implicated in the differentiation of precursor fat cells to the energy-consuming phenotype
  • low testosterone may compound the effect of increasing fat mass by making it more difficult for obese men to lose weight via exercise
  • pro-inflammatory cytokines released by adipose tissue may contribute to loss of muscle mass and function, leading to inactivity and further weight gain in a vicious cycle
  • Sarcopenic obesity, a phenotype recapitulated in men receiving ADT for prostate cancer, [55] may not only be associated with functional limitations, but also aggravate the metabolic risks of obesity;
  • observational evidence associating higher endogenous testosterone with reduced loss of muscle mass and crude measures of muscle function in men losing weight
  • genuine reactivation of the HPT axis in obese men requires more substantial weight-loss
  • A number of intervention studies have confirmed that both diet- and surgically-induced weight losses are associated with increased testosterone, with the rise in testosterone generally proportional to the amount of weight lost
  • men, regardless of obesity level, can benefit from the effect of weight loss.
  • inconsistent effect of testosterone on VAT
  • Nathan Goodyear on 15 Jan 14
     
    to be read
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