AAMC FL #2 B/B question

[ariri]

I don't understand the reasoning behind this question. Background info from the passage is that NPY alone doesn't increase LH, but NPY in addition to GnRH will increase serum LH levels. Answers C and D are obviously wrong, but I don't agree that the GnRH receptor deficient person would benefit more from the LH receptor deficient person. If there are less receptors of LH, wouldn't you want to flood the system with more LH? Isn't this analogous to how we treat Parkinson's Disease? We assume that there is a reduction in dopamine receptors, so we flood the system with more dopamine (pre-cursor to be excact)?

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[desperadoflakes]

Well, no. To be clear about Parkinson's, the pathophysiology is that the cells in the substantia nigra die. These are the cells that produce dopamine. So the treatment with L-DOPA would in fact increase dopamine, alleviating symptoms. As far as I know, the disease progression is not at least initially due to the loss of dopamine receptors at all. If there is loss, it's due to a synaptic or structural potentiation mechanism due to loss of stimulation. This is one hypothesis for why L-DOPA is only effective at the beginning of disease onset.

If you have deficiency in LH receptor, increasing LH production really wouldn't do much for you. This just isn't the way it works. Even if it was, let's think about it. LH is at relatively low levels throughout the cell cycle other than during the LH surge, which only happens after selection of a follicle with high sensitivity to FSH. Increasing GnRH would mean more FSH across the board, so it would be more difficult to select a particularly sensitive follicle. Even if you did, this new secondary follicle now needs to create LH receptors for an LH surge. That LH surge just simply won't happen if those receptors suck.

So much of physiology and especially embryogenesis is reliant on intricate and finely tuned ratios between different hormones and feedback systems. Increasing GnRH just to flood the system with this one hormone that we need in a really specific amount of at a really specific time window doesn't make sense. A GnRH deficient system could be fixed with GnRH, easy peasy

 

[aldol16]

Well, no. To be clear about Parkinson's, the pathophysiology is that the cells in the substantia nigra die. These are the cells that produce dopamine. So the treatment with L-DOPA would in fact increase dopamine, alleviating symptoms. As far as I know, the disease progression is not at least initially due to the loss of dopamine receptors at all. If there is loss, it's due to a synaptic or structural potentiation mechanism due to loss of stimulation. This is one hypothesis for why L-DOPA is only effective at the beginning of disease onset.

This may be interesting: Neuropsychopharmacology - Loss of Dopamine D2 Receptors in Alzheimer's Disease with Parkinsonism But Not Parkinson's or Alzheimer's Disease