Thyroid Hormones
Hormones acting through Nuclear Receptors

Mittag Jens J Clin Invest. Heart brain thyroid

omeprazole thyroid

Comprehensive study of urinary cortisol metabolites in hyperthyroid and hypothyroid patients, 2005

Objective To further analyse the significance and mutual relationship of thyroid function-linked alterations in cortisol metabolism that have been separately and variously reported.

Patients and measurements Twenty-four-hour urine samples from 21 patients with hyperthyroidism (Graves’ disease), 16 patients with hypothyroidism (Hashimoto's thyroiditis), 21 healthy age- and sex-matched controls for hyperthyroidism, and 16 healthy age- and sex-matched controls for hypothyroidism were evaluated for 6β-hydroxycortisol (6β-OHF), tetrahydrocortisol (THF), tetrahydrocortisone (THE), allo-tetrahydrocortisol (allo-THF), urinary free cortisol (UFF), urinary free cortisone (UFE) and 17-hydroxycorticosteroid (17-OHCS).

Results Urinary 17-OHCS, THE and allo-THF levels increased considerably in hyperthyroid patients compared to the controls, while UFF and THF showed no difference between the two groups. Urinary 6β-OHF was significantly lower in the hyperthyroid patients than in the controls. Both the urinary allo-THF + THF/THE and the UFF/UFE ratios were significantly lower in the hyperthyroid patients than in the controls, whereas only the former was significantly higher in the hypothyroid patients than in the controls. The urinary allo-THF/THF ratio was significantly higher in the hyperthyroid patients and significantly lower in the hypothyroid patients than in the controls. In an analysis of pooled subjects including all groups (n = 64), free T4 levels correlated negatively (P < 0·0001) with the urinary allo-THF + THF/THE ratio but not with the UFF/UFE ratio. The serum levels of free T4 correlated positively (P < 0·0001) with the urinary allo-THF/THF ratio.

Conclusion The thyroid hormones seem to affect the total 11β-HSD activity (allo-THF + THF/THE) more strongly than the renal 11β-HSD2 activity (UFF/UFE). 5α-reductase activity (allo-THF/THF) is also enhanced in hyperthyroidism, while the reduction of urinary 6β-OHF in hyperthyroidism might be a secondary effect of the altered activity of the total 11β-HSD and 5α-reductase.
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Think globally: Act locally: New insights into the local regulation of thyroid hormone availability challenge long accepted dogmas, 2008

Amphibian metamorphosis as a model for the developmental actions of thyroid hormone, 2006

The regolation of thyroid function: T3 and T4 production
Thyroxine is synthesised by the follicular cells from free tyrosine and on the tyrosine residues of the protein called thyroglobulin (TG).
Inorganic iodine enters the body primarily as iodide, I-. After entering the thyroid follicle (or thyroid follicular cell) via a Na+/I- symporter (NIS) on the basolateral side, iodide is shuttled across the apical membrane into the colloid via pendrin, after which thyroid peroxidase oxidizes iodide to atomic iodine (I) or iodinium (I+). The "organification of iodine," the incorporation of iodine to thyroglobulin for the production of thyroid hormone is inseparable from oxidation and is catalyzed by TPO. The chemical reactions catalyzed by thyroid peroxidase occur on the outer apical membrane surface and are mediated by hydrogen peroxide. Upon stimulation by the thyroid-stimulating hormone (TSH), the follicular cells reabsorb TG and proteolytically cleave the iodinated tyrosines from TG, forming T4 and T3, and releasing them into the blood. Thyroid hormone that is secreted from the gland is about 90% T4 and about 10% T3.

Deiodinase is an enzyme important in the action of thyroid hormones; it is a selenium-dipendent enzyme. Deiodinases are unusual in that the enzyme contains selenium, in the form of an otherwise rare amino acid selenocysteine.
In the tissues, deiodinases can either activate or inactivate thyroid hormones:
• Activation occurs by conversion of the prohormone thyroxine (T4) to the active hormone triiodothyronine (T3) through the removal of an iodine atom on the outer ring.
• Inactivation of thyroid hormones occurs by removal of an iodine atom on the inner ring, which converts thyroxine to the inactive reverse triiodothyronine (rT3), or which converts the active triiodothyronine to the inactive diiodothyronine (T2). The major part of thyroxine deiodination occurs within the cells.

Thyroid hormones role

Physiological and Molecular Basis

of Thyroid Hormone Action 2001

Impact of placental hormone withdrawal on postpartum depression

In uno studio condotto su 20 donne che presentano una depressione post parto e altre 20 senza depressione post parto, sono stati misurati il livelli di progesterone, estradiolo e l'ormone gonadotropina corionica.

Il risultato è interessante perchè l'effetto depressivo è scatenato da una più veloce perdita dell'ormone gonadotropina corionica nelle donne affette da depressione rispetto a quelle senza depressione post parto.

L'effetto depressivo potrebbe essere quindi correlato alla mancanza di TSH dovuto ad una troppo veloce perdita dell'ormone gonadotropina corionica (che durante la gravidanza vicaria l'azione del TSH facendo produrre tanto ormone tiroideo).
Se manca l'ormone tiroideo mancherà alle cellule ATP....SNC meno vivace!

Medpilot thyroid+hormone+receptor+aging

Expression of thyroid hormone receptors A and B in developing rat tissues; evidence for extensive posttranscriptional regulation. 2007

TH and lipoproteins

Beneficial effects of a novel thyromimetic on lipoprotein metabolism. 1997

THYROMIMETIC LIPOPROTEIN

Thyroid hormones and thyroid hormone receptors: effects of thyromimetics on reverse cholesterol transport.2010 Fulltext
World J Gastroenterol. 2010 Dec 21;16(47):5958-64.
Pedrelli M, Pramfalk C, Parini P.

Reverse cholesterol transport (RCT) is a complex process which transfers cholesterol from peripheral cells to the liver for subsequent elimination from the body via feces. Thyroid hormones (THs) affect growth, development, and metabolism in almost all tissues. THs exert their actions by binding to thyroid hormone receptors (TRs). There are two major subtypes of TRs, TRα and TRβ, and several isoforms (e.g. TRα1, TRα2, TRβ1, and TRβ2). Activation of TRα1 affects heart rate, whereas activation of TRβ1 has positive effects on lipid and lipoprotein metabolism. Consequently, particular interest has been focused on the development of thyromimetic compounds targeting TRβ1, not only because of their ability to lower plasma cholesterol but also due their ability to stimulate RCT, at least in pre-clinical models. In this review we focus on THs, TRs, and on the effects of TRβ1-modulating thyromimetics on RCT in various animal models and in humans.

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voce bibliografica

On commonness and rarity of thyroid hormone resistance: A discussion based on mechanisms of reduced sensitivity 2007

Decrease in mitochondrial energy coupling by thyroid hormones: a physiological effect rather than a pathological hyperthyroidism consequence. 1998 Fulltext

Under the same conditions, 6-ketocholestanol appeared to be effective in recoupling of respiration uncoupled by low concentrations of the artificial protonophore FCCP.