Thyroid hormone plays significant role in cardiac remodeling after acute myocardial infarction. Thyroid hormone, particularly T3 as the vast majority of T3 is produced in heart tissue via D1 enzymatic activity, improves cardiac contractility, reduces systemic vascular resistance, reduces cardiac work load, decreases blood pressure, improves cardiac metabolism, and thus improves outcomes post MI.
Thyroid treatment in those with hypothyroidism and insulin resistance provided no benefit to the insulin resistance. But, Total cholesterol did improve.
SHBG decreases in response to androgens, and in the presence of hypothyroidism, and insulin resistance.
Plasma SHBG levels tend to increase with increasing age
The apparent metabolic clearance rate of testosterone is decreased in elderly as compared to younger men
Testosterone circulates predominantly bound to the plasma proteins SHBG and albumin, with high and low affinity respectively
Testosterone is secreted in a pulsatile fashion
Current clinical guidelines suggest at least two measurements
In adult men, there is a well-documented diurnal variation (particularly in younger subjects) in testosterone levels, which are highest in the early morning and progressively decline throughout the day to a nadir in the evening
In older men, the diurnal variation is blunted
it is standard practice for samples to be obtained between 0800 and 1100 h.
Testosterone and DHEA decline, whereas LH, FSH, and SHBG rise
DHT remains constant despite the decline of its precursor testosterone
Longitudinal studies show an average annual decline of 1–2% total testosterone levels, with decline in free testosterone more rapid because of increases in SHBG with aging
Massachusetts Male Aging Study (MMAS) data show DHEA, DHEAS, and Ae declining at 2–3% per year
DHT showed no cross-sectional age trend
Androstanediol glucuronide (AAG) declined cross-sectionally with age in the MMAS sample, at 0.6% per year
The EMAS data show that, consistent with the longitudinal findings of MMAS (Figure 1), the core hormonal pattern with increasing age is suggestive of incipient primary testicular dysfunction with maintained total testosterone and progressively blunted free testosterone associated with higher LH
This author proves the point in the review of these two studies, that TT may remain constant in aging men, however, FT drops.
obesity impairs hypothalamic/pituitary function
Androgen deprivation in men with prostate cancer has been associated with increased insulin resistance, worse glycemic control, and a significant increase in risk of incident diabetes
Low serum testosterone is associated with the development of metabolic syndrome 116, 117 and type 2 diabetes. 118 SHBG has been inversely correlated with type 2 diabetes
Improvement in insulin sensitivity with testosterone treatment has been reported in healthy 121 and diabetic 122 adult men
In studies conducted in men with central adiposity, testosterone has been shown to inhibit lipoprotein lipase activity in abdominal adipose tissue leading to decreased triglyceride uptake in central fat depots. 123
which is a major reason for the regaining of lost weight with dieting as well being the mechanism behind stress induced weight gain (it is not due to increased cortisol).
f greater than 10, it demonstrates there is a degree of leptin resistance contributing to an inability to lose weight
that it is difficult to lose weight with leptin resistance. High carbohydrate diets and in particular high-fructose corn syrup is shown to significantly increase leptin resistance and is a likely mechanism that high fructose corn syrup is associated with obesity
it is problem inside the cell that the inactive T4 is not converted to T3 but rather to a mirror image of T3 called reverse T3. The reverse T3 has the opposite effect of T3, blocking the effects of T3 and lowering rather than increasing metabolism.
Studies are showing that stress and dieting (especially yo-yo dieting) can set this hormone into action as well as chronic illness such as diabetes, chronic fatigue syndrome and fibromyalgia.
As soon as the body senses a reduction in calories, the production of reverse T3 is stimulated to lower metabolism
With chronic dieting or stress, the body often stays in this "starvation mode" with elevated levels of reverse T3 and decreased levels of T3, which is a major reason for the regaining of lost weight with dieting as well being the mechanism behind stress induced weight gain (it is not due to increased cortisol).
which is a major reason for the regaining of lost weight with dieting as well being the mechanism behind stress induced weight gain (it is not due to increased cortisol).
which is a major reason for the regaining of lost weight with dieting as well being the mechanism behind stress induced weight gain (it is not due to increased cortisol).
Studies are showing that such standard testing will miss 80% of thyroid dysfunction
tissue euthyroidism is the net result of multiple steps including conversion of the prohormone T4 into its active metabolite T3, which is ultimately responsible for signaling at the end-organ target level
The circulating and intracellular pools of T3 of treated hypothyroid patients (i.e. devoid of endogenous TH production) depend entirely on the conversion of exogenous l-T4 into T3
The substitution of l-T3 for l-T4 caused a significant weight loss
The substitution of l-T3 for l-T4 caused a significant reduction in lipid parameters
TH action is increased in the liver, and the SHBG increase supports this hypothesis
The changes in serum lipid metabolism parameters are similar to the effects observed with drugs approved for the treatment of dyslipidemia
This differential response appears to be limited to the lipid metabolism and SHBG, whereas no differences in indices of insulin resistance were detected. This is remarkable because hyperthyroid states are associated with an increase in hepatic gluconeogenesis (37), and overt thyrotoxicosis is a known cause of secondary diabetes.
Despite the increase in serum T3, the l-T3 treatment did not cause major changes in cardiovascular or musculoskeletal function, as indicated by the echocardiographic and maximal exercise tolerance tests and DXA studies.
Similarly, no significant differences were observed in blood pressure, heart rate, or endothelial vascular function
In conclusion, the results of this pharmacology, proof-of-concept study indicate that replacement therapy of hypothyroidism with l-T3, compared with l-T4 causes weight loss and favorable changes in the lipid profile without appreciable side effects
Crossover study finds T3 versus T4 results in more weight loss, improved lipid management and increased SHBG without any adverse cardiovascular effects. The T3 was dosed 3 x daily due to its short half life compared to T4.