Mechanism of Hormone Action

The hormonal mechanisms of action to regulate glycogenesis and glycogenol-ysis involve reversible phosphorylation of the critical enzymes glycogen synthase and phosphorylase, respectively (Figure 6—6). 

Thyroid hormone mechanisms of action can be classified into two types (1) genomic or nuclear and (2) nongenomic, including effects at the plasma membrane and mitochondria. Genomic effects involve modification of gene transcription, are mediated only by Tj, and require at least several hours to detect. Nongenomic actions are generally rapid in onset and occur in response to T4 and some T4 metabolites (e.g., rT3,T3, and Tj). 

See also Hormone Action, Hormone Mechanisms of Action, Hormone Hierarchy of Action, Receptors with Protein Kinase Activity, Steroid and Thyroid Hormones - Intracellular Receptors, Action of Insulin, Action of Glucagon, Action of Epinephrine... 

See also G Proteins and Signal Transduction, Hormone Mechanisms of Action, Guanylate Cyclase... 

Considering the relative simplicity of the molecular structure of steroid hormones and the huge amount of work devoted to studying these hormones mechanism of action, one would hope to be able to present a lucid explanation of the mechanism of action. Yet, we are still far from such a proposition, and unless a dramatic breakthrough occurs within a short time, the solution is not within our reach. The student should therefore not anticipate a description of the pathogenesis of the diseases of the sex glands in molecular terms. 

No postulated hormone mechanism of action, with the possible exception of the Sutherland model of glycogenolysis activation by adrenaline, has yet fully satisfied all these criteria. 

Mechanism of Action. Eew data are available that describe the effects of anaboHc steroids on protein metaboHsm even fewer data exist for assessment of direct effects of anaboHc steroids on Hpid metaboHsm in growing mminants. The lack of any consistent change in somatotropin, prolactin, insulin, or other metaboHc hormones (qv) in a total of 15 studies has been noted (1,38). 

Drugs with unknown mechanism of action are gabapentin, bromides (but see above effects on GABAergic transmission) and adrenocorticotropic hormone (ACTH), which is used in infantile spasms. 

The mechanisms by which the growth supplements in serum-free medium act are still not understood. In order to achieve an understanding of the biochemical basis for the hormonal and growth factor requirements of animal cells, the basic mechanism of action of hormones and growth factors must be determined. The biochemical basis for the nutritional requirements of animal cells can only be determined when we have an understanding of the metabolism of the different types of animal cells. 

Flototto, T. Djahansouzi, S. Glaser, M. Hanstein, B. Niederacher, D. Brumm, C. Beckmann, M. W. Hormones and hormone antagonists mechanisms of action in carcinogenesis of endometrial and breast cancer. Horm. Metab. Res. 2001, 33, 451 -57. 

Fulvestrant is a new agent approved for the second-line therapy of postmenopausal metastatic breast cancer patients who have tumors that are hormone-receptor-positive. Studies examining the role of fulvestrant in the treatment of metastatic breast cancer have compared this agent with anastrozole. Given anas-trozole s mechanism of action, only postmenopausal women were eligible for these trials. There is no biologic reason why fulvestrant should not produce similar outcomes in premenopausal... 

---