Sex Steroids and the Thyroid

Thyroid function is modulated by genetic and environmental causes as well as other illnesses and medications such as gonadal or sex steroids. The latter class of drugs (sex steroids) modulates thyroid function. Gonadal steroids exert their influence on thyroid function primarily by altering the clearance of thyroxine-binding globulin (TBG). While oestrogen administration causes an increase in serum TBG concentration, androgen therapy results in a decrease in this binding protein. These effects of gonadal steroids on TBG clearance and concentration are modulated by the chemical structure of the steroid being used, its dose and the route of administration. Despite the gonadal steroids-induced changes in serum TBG concentrations, subjects with normal thyroid glands maintain clinical and biochemical euthyroidism without changes in their serum free thyroxine (T4) or thyroid-stimulating hormone (TSH) levels. In contrast, the administration of gonadal steroids to patients with thyroid diseases causes significant biochemical and clinical alterations requiring changes in the doses of thyroid medications. Similarly, gonadal steroid therapy might unmask thyroid illness in previously undiagnosed subjects. It would be prudent to assess thyroid function in subjects with thyroid disease 6-8 weeks after gonadal steroid administration or withdrawal.

Rundsarah Tahboub et al. Best Pract Res Clin Endocrinol Metab. Dec 2009

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Another direct link between estrogen levels and TBG.

The Effects of Sex-Steroid Administration on the Pituitary-Thyroid Axis in Transsexuals

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Objective: Estrogen and androgen administration modulate the pituitary-thyroid axis through alterations in thyroid hormone-binding globulin (TBG) metabolism, but the effects of sex steroids on extrathyroidal thyroxine (T4) to triiodothyronine (T3) conversion in humans are unknown.

Design and methods: We studied 36 male-to-female and 14 female-to-male euthyroid transsexuals at baseline and after 4 months of hormonal treatment. Male-to-female transsexuals were treated with cyproterone acetate (CA) 100 mg/day alone (n = 10) or in combination with either oral ethinyl estradiol (or-EE) 100 microg/day (n = 14) or transdermal 17beta-estradiol (td-E) 100 microg twice a week (n = 12). Female-to-male transsexuals were treated with i.m. testosterone 250 mg twice a week. A t-test was used to test for differences within groups and ANOVA with post hoc analysis to test for differences between the groups.

Results:
Or-EE increased TBG (100 +/- 12%, P < .001) and testosterone decreased TBG (-14 +/- 4%, P = 0.01), but free T4 did not change. Td-E and CA did not affect TBG concentrations. TSH was not different between groups at baseline or after treatment. CA decreased T3/T4 ratios (-9 +/- 3%, P = 0.04), suggesting that T4 to T3 conversion was lower. Testosterone increased T3/T4 ratios (30 +/- 9%, P = 0.02), which probably reflects higher T4 to T3 conversion.

Conclusion:
Oral but not transdermal estradiol increases TBG, whereas testosterone lowers TBG. Testosterone increases T3/T4 ratios. Estradiol does not affect T3/T4 ratios, irrespective of the route of administration.

In my mind this supports my theory of the test in a test and tren cycle, when converted to estradiol at a high rate can increase TBG enough to cause lethargy, tiredness. Sleepiness. This could often be confused as going hypo or even more, may be in conjunction with. Those two things together assuredly would make you feel like hammered shit.

As one of the distasteful side effects of steroids or other strong testosterone-enhancers, the negative effects of reduced sex drive and sperm count were on the top of the list when making SARMs. The producers of SARMs wanted to design a supplement that gave all the great benefits of steroids, while still specifically promoting full anabolic activity muscle and bone.

“It is unquestionable that some patients will tell you that the day they were switched from levothyroxine to combination therapy, ‘a light bulb went on in my brain,’ or ‘I can think again.’ There has got to be something there,” says Antonio C. Bianco, MD, PhD, professor of medicine and vice dean of clinical affairs at Rush University Medical Center in Chicago, Illinois.

Dean Destructo said:

“It is unquestionable that some patients will tell you that the day they were switched from levothyroxine to combination therapy, ‘a light bulb went on in my brain,’ or ‘I can think again.’ There has got to be something there,” says Antonio C. Bianco, MD, PhD, professor of medicine and vice dean of clinical affairs at Rush University Medical Center in Chicago, Illinois.

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Dean, can yopu elaborate on what you mean here or what they mean with this statement? Im not following the "light bulb" comment