Steroid Hormone and Thyroid Hormone Mechanisms of Action

Steroid Hormone and Thyroid Hormone Mechanisms of Action

Author: Aaron Mullally

- know how steroid hormones and thyroid hormones interact with cells

- know the step of non-polar hormone actions

- know which hormones utilize this form of action

This packet covers how non-polar chemical messages interact with cells

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Steroid and Thyroid Hormone Actions

Even though steroid hormones and thyroid hormones are synthesized from different biological products they do have one thing in common, they are non-polar (not charged). Having this chemical property allows them to cross the plasma membrane and directly interact with cells. Essentially these hormones influence the protein synthesizing processes of the cell. Actions of steroid hormones are slower than that of their polar counterparts. Here are the steps of action:

  1. the hormone crosses the plasma membrane into the cytstol of the cell
  2. the hormone binds with nuclear receptors on the nuclear envolope
  3. the binding exposes the receptor to its DNA-binding domain and SRE's are created (SRE = steroid-response elements)
  4. The SRE acts as a transcription factor and effects the rate of mRNA production
  5. mRNA leaves the nucleus and interacts with ribosomes
  6. new proteins are synthesized
  7. action occurs

As mentioned earlier this type of response is much slower. It takes more time to synthesize new proteins, modify them and then put them to use. Secondary messenger systems are more like flipping a light switch; all of the components are in place, all that's needed is a finger (hormone) to flip the switch and turn it on and off (separating the hormone & receptor)

Here is a useful link to see this in action: http://www.physiol.med.uu.nl/interactivephysiology/ipweb/systems/buildframes.html?endocrine/acthorm/01

Source: Mind of Aaron

Steroid Hormone Actions

This video covers how steroid hormones interact with cells

Source: Self made