Hormone-receptor-initiated cellular processes

Once thyroid hormone enters a cell, it binds temporarily with a spt plasmic protein. Thyroid hormone molecules migrate to the nucleus chondria, where they bind to receptors. In the nucleus the binding hormone initiates the transcription of genes that play crucial roles i of cellular processes, such as those that code for growth hormone a ATPase. In mitochondria, thyroid hormones promote oxygen consur increased fatty acid oxidation. (The mechanism by which this latter pro< is not understood.)... 

Figure 10.1 ThecyclicAMPsecondmessengersystem.Themostcommonsecond messenger system activated by the protein/peptide hormones and the catecholamines involves the formation of cAMP. This multistep process is initiated by binding of the hormone (the first messenger) to its receptor on the cell surface. The subsequent increase in the formation of cAMP (the second messenger) leads to the alteration of enzyme activity within the cell. A change in the activity of these enzymes alters cellular metabolism.

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