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Nathan Goodyear

Bisphenol A may cause testosterone reduction by adversely affecting both testis and pit... - 0 views

www.sciencedirect.com/...S0378427410000561

testosterone Bisphenol-A Bisphenol A BPA low T leydig cells pituitary

shared by Nathan Goodyear on 01 Feb 12 - No Cached
  • Nathan Goodyear on 01 Feb 12
     
    Bisphenol-A inhibits testosterone production through direct inhibition of the pituitary and the leydig cells.  This is similar to the way E2 acts on the the pituitary and the leydig cells.  
Nathan Goodyear

LPS-Induced Inflammation Potentiates the IL-1-Mediated Reduction of LH Secretion from t... - 0 views

www.hindawi.com/...926937

inflammation luteinizing hormone LH hypothalamus pituitary Testosterone LPS IL-1beta

shared by Nathan Goodyear on 03 Mar 15 - No Cached
  • Nathan Goodyear on 03 Mar 15
     
    IL-1beta reduced GNRH and LH production at the level of the Hypothalamus and the Pituitary respectively. What is interesting in this animal model is that greater LH suppression at the pituitary was found to occur in those animals with prior LPS exposure--priming??
Nathan Goodyear

Does Cortisol Inhibit Pulsatile Luteinizing Hormone Secretion at the Hypothalamic or Pi... - 0 views

press.endocrine.org/...en.2003-1114

cortisol stress LH pituitary hypothalamus GnRH hormone hormones

shared by Nathan Goodyear on 02 Apr 15 - No Cached
  • Nathan Goodyear on 02 Apr 15
     
    Cortisol inhbits LH secretion at the level of the Pituitary.  The result is a decreased pulse amplitude as a result of decreased pituitary response to GNRH.
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

Neuroendocrine disorders after... [J Neurol Neurosurg Psychiatry. 2008] - PubMed - NCBI - 0 views

www.ncbi.nlm.nih.gov/...18559460

PTHP traumatic brain injury TBI neuroendocrine post-traumatic hypopituitarism brain injury neurology hormone hormones pituitary hypothalamus psychiatry

shared by Nathan Goodyear on 09 Jul 12 - No Cached
  • Nathan Goodyear on 09 Jul 12
     
    The majority of people with PTHP after TBI remain undiagnosed.  The current thought, is that 25% of those with TBI have at least one pituitary hormone deficiency.  It does not have to be total pituitary failure.  Deficiencies can be isolated.
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

Occurrence of pituitary dysfunction following ... [J Neurotrauma. 2004] - PubMed - NCBI - 0 views

www.ncbi.nlm.nih.gov/...15253797

HGH pituitary dysfunction TBI traumatic brain injury human growth hormone hormones

shared by Nathan Goodyear on 03 Feb 12 - No Cached
  • Nathan Goodyear on 03 Feb 12
     
    pituitary dysfunction found in people with TBI.  This study found the greatest effect on HGH.
Sundhar krishna

Pituitary Tumor Removal India at Affordable Cost - 0 views

www.biggestclassifieds.com/index.php

endoscope skull base surgery endocrinologist craniotomy neuro ophthalmologist pituitary gland tumours glomus tumors adenoma removal nasal cerebello pontine angle tumour sphenoid sinus treatment endoscopic csf leak repair fungal sinusitis fibrous dysplasia

shared by Sundhar krishna on 19 Jul 12 - No Cached
  • Sundhar krishna on 19 Jul 12
     
    Krishna Eye and Ent is one of the best hospital for skull base surgery India. We offer treatment for tumors like pituitary gland tumours, glomus tumors, cerebello pontine angle tumour and treatment for fungal sinusitis, endoscopic csf leak repair.
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

Hypothalamic-Pituitary-Testicular Axis Disruptions in Older Men Are Differentially Link... - 0 views

press.endocrine.org/...jc.2007-1972

low T low Testosterone low T Testosterone aging LH hormone hormones men male SHBG

shared by Nathan Goodyear on 03 Sep 14 - No Cached
  • 0.4–2% annual decline
  • the age trend in free T was more substantial (−1.3% per annum)
  • The core hormonal pattern with increasing age is suggestive of incipient primary testicular dysfunction with maintained total T and progressively blunted free T associated with higher LH.
  • ...16 more annotations...
  • Obesity was associated with progressively lower total and free T independent of the simultaneous decrease in SHBG.
  • our data highlight the fact that LH was unchanged or even lower in older men in the face of lower T in obesity, suggesting that there may be a failure at the hypothalamic-pituitary level.
  • a change in BMI from nonobese to obese may be equivalent to a 15 yr fall in T.
  • This pattern supports the hypothesis that different underlying mechanisms influence the functions of the HPT axis: age predominantly affects testicular function, whereas obesity impairs hypothalamic/pituitary function.
  • the effects of aging on testicular function can be moderated by increased LH compensation for many decades
  • obesity impairs hypothalamic/pituitary function independent of age, arguably an adaptive response for which there should be no compensatory mechanism.
  • the concurrent but opposite (and separate) effects of obesity and age on SHBG
  • SHBG was negatively associated with increasing strata of obesity
  • Obesity is associated with insulin resistance (28), and the increased circulating insulin inhibits hepatic SHBG synthesis
  • the SHBG increase with age may be related to relative IGF-I deficiency (27), although this has not been directly proven.
  • Obesity is associated with peripheral and central insulin resistance (30) and proinflammatory cytokine production (TNFα and IL-6) from adipocytes (31) and central nervous system endocannibinoid release (32), all of which are potential candidates for abrogating hypothalamic endocrine and downstream reproductive axis functions.
    • Nathan Goodyear
      Nathan Goodyear on 03 Sep 14
       
      The HPA axis effect may be the result of inflammation.
  • The relationship between obesity and T can be bidirectional: low T may be the cause rather than consequence of obesity
  • chronic alcohol abuse is known to suppress LH (40), our data showed no significant association among the three hormones or SHBG and alcohol intake.
  • increase in total T in smokers occurs through a primary increase in SHBG with a compensatory rise in LH
  • the effects of obesity (BMI or waist circumference) was by far the most important determinant of variance in total T, whereas age per se was important for SHBG, LH, and free T with comorbidity and smoking being comparatively minor contributors
  • It is noteworthy that these predisposing lifestyle and health factors are modifiable. This implies that the apparent age-related decline in T may constitute a barometer of health and thus be potentially preventable and/or reversible.
  • Nathan Goodyear on 03 Sep 14
     
    Age induced decline in Testosterone is more associated with a decline in leydig cell function and thus elevated LH will be associated.  In contrast, obesity is more of a HPA axis disruption and thus LH may be normal to low.  The pulse amplitude is decrease.  No change in pulse frequency is noted.   With obesity, a decline in TT and fT was independent of SHBG. Aging is associated with a greater decrease in fT versus TT.
Nathan Goodyear

Exposure of Newborn Male and Female Rats to Environmental Estrogens: Delayed and Sustai... - 0 views

endo.endojournals.org/...4512.long

xenoestrogen xenoestrogens ER alpha ER-beta estrogen receptor estrogen receptor alpha estrogen receptor beta estrogen receptor receptors hormone hormones pituitary environmental

shared by Nathan Goodyear on 07 Jan 13 - No Cached
  • Nathan Goodyear on 07 Jan 13
     
    xenoestrogen exposure has been shown to increase ER alpha and ER beta in the pituitary.
Nathan Goodyear

Effect of vasopressin 1b receptor blockade on the hypothalamic-pituitary-adrenal respon... - 0 views

joe.endocrinology-journals.org/...285.full.pdf

stress HPA hypothalamus pituitary axis hypothalamic-pituitary chronic CRH AVP vasopressin

shared by Nathan Goodyear on 03 Oct 12 - No Cached
  • Nathan Goodyear on 03 Oct 12
     
    repeated stress results in down regulation of central stress response ie. blunted CRH response.
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

Hypothalamopituitary Dysfunction Following Traumatic Brain Injury and Aneurysmal Subara... - 0 views

jama.ama-assn.org/...1429.full

TBI traumatic brain injury pituitary HPA hormone hormones hypothalamic dysfunction

shared by Nathan Goodyear on 03 Feb 12 - No Cached
  • Nathan Goodyear on 03 Feb 12
     
    TBI results in altered pituitary function.  This study reviewed research articles published over a 7 year time (2000-2007).
Nathan Goodyear

Decreased Basal and Stimulated Thyrotropin Secretion in Healthy Elderly Men - 0 views

jcem.endojournals.org/...177.abstract

TSH TRH aging men elderly thyroid hormone T3 T4 pituitary

shared by Nathan Goodyear on 07 Feb 12 - No Cached
  • Nathan Goodyear on 07 Feb 12
     
    This study shows that older men are associated with low TSH, reduced response to TRH, lowered T3, and normal T4 levels.  The main find in this study was the decrease in pituitary responsiveness to TRH and the reduced TSH as we age.  TSH is unreliable as a test.
Nathan Goodyear

Prevalence of Neuroendocrine Dysfunction in Patients Recovering from Traumatic Brain In... - 0 views

jcem.endojournals.org/...2752.full

TBI traumatic brain injury HGH pituitary cortisol thyroid hypothyroid hypothyroidism

shared by Nathan Goodyear on 03 Feb 12 - No Cached
  • Nathan Goodyear on 03 Feb 12
     
    TBI results in pituitary dysfunction.  The result in low cortisol, low thyroid, and low HGH.  Other hormones appeared to be unaffected
Nathan Goodyear

PsychiatryOnline | The Journal of Neuropsychiatry and Clinical Neurosciences | The Neur... - 0 views

neuro.psychiatryonline.org/article.aspx

TBI traumatic brain injury pituitary neuroendocrine deficits injury brain sex hormone HGH growth

shared by Nathan Goodyear on 03 Feb 12 - No Cached
  • Nathan Goodyear on 03 Feb 12
     
    TBI results in hormone disruption in 25-69% of those effected.  The major cause is a pituitary/neuro-endocrine effect.  This has been described since the early 20th century.
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

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
Nathan Goodyear

HPA axis changes during the initial phase of psychosocial stressor exposure in male mice - 0 views

joe.endocrinology-journals.org/...193.abstract

HPA stress cortisol pituitary metabolism hormone hormones

shared by Nathan Goodyear on 24 Jul 13 - No Cached
  • Nathan Goodyear on 24 Jul 13
     
    Stress response in a animal model is blunted at the level of pituitary through a decrease in ACTH release and through increase in peripheral metabolism
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