The buspirone challenge test clearly distinguishes ME/CFS patients from healthy controls: why is it not being developed and deployed?

Could an imbalance of the short and long forms of prolactin receptors mean that some cells are going into apoptosis or be otherwise misbehaving in some way? Perhaps they’re responding badly to perfectly normal signals?

Could the increase that we see in response to Buspirone be a result of the body over compensating to this and trying to get a signal to somewhere and it's just not being heard so it shouts louder? Maybe some subset of cells up or down regulating in response to this imbalance of receptors elsewhere?
 
I was also wondering if any of these studies tested macroprolactin.

“Macroprolactin is a large, inactive complex formed when the hormone prolactin binds to an antibody (usually IgG). Because standard blood tests measure total prolactin, macroprolactin can cause a false-positive high prolactin”
 
Jaybee00 said:
Flow chart from @forestglip paper from chat GPT. Does this look ok? Please edit if not OK. Thanks @forestglip

If it looks OK, I may send to OMF along with the review.

p.s. I have no idea how to edit these things.


View attachment 33887
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I think now that it’s been all finalized a git repo would serve well, that way you can see revisions to the document, push major revisions as a release. This flow chart could be a mermaid .md diagram that is easily edited
 
Jaybee00 said:
Flow chart derived from @forestglip paper from chat GPT. Does this look ok? Please edit if not OK. Thanks @forestglip

If it looks OK, I may send to OMF along with the review.

p.s. I have no idea how to edit these things.


View attachment 33887
Click to expand...
I'm not quite sure this is the right approach, unless the review is the focus and this is just suggested as draft of possible next steps. @forestglip has written a detailed summary of the problem and possible next steps that are worthwhile and what explorations could follow and how.

I don't think competent investigators should be told what to do next, they should bring in competence to do exactly that, otherwise it's not going to lead anywhere to begin with. They have to understand what the question is and then figure out how to answer it.
 
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Jaybee00 said:
Flow chart is 100% derived from @forestglip text. I did zero editing.
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The chart looks pretty and is easy to understand. It is well made. It's fantastic that you're reaching out to people and thinking about how to do that! To me the review is the relevant part. It captures previous experiments and data. As such it encapsulates the questions that need to be answered. If you have to tell someone how to answer the question there's no point in doing so because they haven't even understood the question yet, you cannot teach a blind man to see.

Maybe it is nice to forward this with the review as well and it may be useful on social media as an example of next steps because it's a simple visualisation, but I don't think it should be prominently featured when approaching someone.
 
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ChronicallyOverIt said:
macroprolactin can cause a false-positive high prolactin
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I was wondering about this. Do you have a source? Could be mentioned in our list of suggested things that a future study may want to test for/rule out as the cause.

@Jaybee00 your idea to share the doc with OMF sounds great. I would strongly suggest holding off on sending the AI graphic because it has turned some of forestglip’s carefully hedged statements into confident interpretations that as @EndME says we’d really like some expert help with. We’d also really like to encourage less jumping to conclusions than has historically been the case in this.
 
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Jaybee00 said:
Flow chart derived from @forestglip paper from chat GPT. Does this look ok? Please edit if not OK. Thanks @forestglip

If it looks OK, I may send to OMF along with the review.

p.s. I have no idea how to edit these things.


View attachment 33887
Click to expand...

I think that the point of being careful about which drugs and whether 'matched pairs' and other methodological aspects are used are because it so far indicates that it is just buspirone, d-fenfluramine and not serotinin 'in general' causing a spike .... YET historically this perhaps got lost because those testing it were just looking quite simplistically at assuming those with serotonin in were 'serotinin caused' and even thought that buspirone was a proxy for testing 'sensitivity to serotonin' even when there were some responses in the peer review talking about certain drugs being 'dirty' ie not that straightforward.

So on the decision chart it is more about testing eg buspirone vs d-fenfluramine and not 'does serotinin work' does 'dopamine work' and if one does and the other doesn't because the drugs aren't just those but also because it is a case of comparing the reactions in the drugs that are more 'dirty' I guess.

Plus both pure dopaminagenic (and potentially serotonigenic for pwme) come with real risks and issues. It might be useful to rule-in/out have comparators of the impact of the more pure version

but it comes down to issues with controlling for a range of issues with pwme in methodology and in recruitment. Things that relate to exertion for us cause spikes in prolactin in normal people (over-exertion being one, sleeplessness that also relates to over-exertion, heat etc), every individual has a different severity level + situation/things that cause issue (eg noise vs sitting uncomfortably vs other comorbidities, being further distances from 'the lab' having a hectic time etc) - yet just 'getting the same person' doesn't then make them a matched pair for themself because of that too due to PEM/medium-longer term impact of the exertion of each of these.

I'd even throw in that knowing what we know now about some of these wider drugs depending on the methodology even controls gets tricky - and certainly making sure it is externally valid rep of the population given we have migraine etc and other illnesses (and RLS is linked to dopamine, many other things to serotonin) and method of recruitment might well pick up 'controls' who have other things in a poster for ME/CFS more than certain other illnesses?

I think that doing this sort of thing 'right' will help, I'm not sure repeating the issues in a circle everyone went round for what looks like over a decade is a good idea.

I do think that scan possibilities have moved on massively given that fMRI's back in the late 90s were things a uni would show off about having in their brochure as a 'big thing' and I'd hope techniques and knowledge have grown on those and other options. Maybe @SNT Gatchaman can point if there is some new magic option/advice on whether scans can offer things today?

From what I get you can't just use a scan to see these receptors working or which ones are being blocked and how many of them are there getting the brake put on by running a scan, certainly not without knowing what it is you'd be looking for as an indicator of this and getting the timings right etc. the brain is tricky like that. And it seems to be the drugs were a lot is going on /are 'dirty' that are the ones with the effects which


ME/CFS Science Blog said:
Yeah maybe the dopamine system in ME/CFS is less responsive so that those natural stimuli that reduce it centrally have less impact and thus we see a blunted prolactin response.

But when you don't impact the dopamine system itself but simply block the dopamine that's already there, we see an exaggerated response because the lactotrophs had compensated by being more responsive to changes.
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this is the bit I'm trying to think around. So in buspirone where the effect could be direct from antagonist on D2, 3, 4 receptor (?) leading to much larger spike in prolactin that controls (and I guess both the 'peak' size and overall amount of prolactin is interesting here). Is it that the difference is in blocking 'more' of the receptors in ME/CFS or that the reaction (prolactin release) is more exaggerated/immediate when the same amount of 'blocking' of the same ratio of receptors occurs?

If that causes drop in dopamine which in turn causes increase in prolactin release then is it the dopamine drop [causing a faster or bigger 'brake'] or the size of prolactin release in response to the same size of dopamine drop [brake]

and then d-fenfluramine has an indirect effect but it is on the D1 receptor?
 
Jaybee00 said:
Flow chart derived from @forestglip paper from chat GPT. Does this look ok? Please edit if not OK. Thanks @forestglip
Click to expand...

I could see how there might be some benefit in the visual just to grab people's attention to even read the review. Though I might lean towards saying that what it's showing isn't really the important part, as others said. My ideas for what to do next are just amateur musings, and I'm sure experts can come up with better tests. The really interesting part that is important to get across is that abnormally high prolactin response was seen over and over and over and over and over and over, every time anyone tested it.

There might also be a possibility it'd give an AI vibe that might make people less confident of the information being shared.

But just mentioning a couple issues with the flow chart: step 2 is testing domperidone, a dopamine antagonist. But step 1 is already about testing a dopamine antagonist, so it could just be part of step 1. There's also no option for if only a dopamine antagonist or only TRH leads to an increased prolactin response (to be fair, my review didn't include that either, but in a flow chart it might be especially important to aim for completeness).

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I am thinking more and more that the reason this was not pursued further was because most of the authors of the old papers were highly confident that it already told them all they needed to know: something like up-regulation of serotonin receptors. Once they saw two studies finding increased prolactin response to a specific serotonin agonist (d-fenfluramine), they had their answer. Why no one seemed to be considering that the abnormality might be something downstream of the receptors the drugs bound to, I do not know.

So the main things I want to get across with all this are: 1) the prolactin response finding is one of the most replicated in ME/CFS research, and 2) the implication of the finding is probably not nearly as clear as all the papers made it out to be, and this is the reason it needs to be revisited and tested from various other angles.

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Putting on my amateur musing hat again: I think a lot could potentially be done with a single patient, and maybe it could be done much faster than assembling a big new study. Some of the studies were finding ME/CFS prolactin responses far above what healthy individuals showed. When lab findings are nowhere near what you expect for healthy people, you can learn a lot without needing the statistical power of large groups. The hope is that whatever patient would volunteer would be one of those with a highly abnormal response, and that ideally other test findings would be very abnormal as well, like maybe prolactin response to TRH.

It might just take a motivated clinician-researcher and a patient who is willing to be a bit of a guinea pig (and a dollop of ethics approval and a spoonful of cash). The case study on the patient would provide motivation to replicate whatever is found in an actual case-control study of ME/CFS.
 
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bobbler said:
this is the bit I'm trying to think around. So in buspirone where the effect could be direct from antagonist on D2, 3, 4 receptor (?) leading to much larger spike in prolactin that controls (and I guess both the 'peak' size and overall amount of prolactin is interesting here). Is it that the difference is in blocking 'more' of the receptors in ME/CFS or that the reaction (prolactin release) is more exaggerated/immediate when the same amount of 'blocking' of the same ratio of receptors occurs?

If that causes drop in dopamine which in turn causes increase in prolactin release then is it the dopamine drop [causing a faster or bigger 'brake'] or the size of prolactin release in response to the same size of dopamine drop [brake]
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These are all questions that probably still need to be tested to be sure.

Some studies of ME/CFS and migraine were suggesting overly sensitive dopamine receptors (though what exactly that means isn't clear - maybe more of them). However, estrogen also causes a larger prolactin response, but it seems to do so through the opposite route when given to animals: making the cells less sensitive to dopamine. So maybe what's happening in ME/CFS is more like that.

bobbler said:
and then d-fenfluramine has an indirect effect but it is on the D1 receptor?
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D-fenfluramine (or actually its metabolite norfenfluramine) actually mainly binds to serotonin (5-HT) receptors, not dopamine receptors. So it probably binds to some cells in the hypothalamus, and those cells either directly tell the pituitary to release more prolactin, or go on to tell other cells to talk to the pituitary. On the other hand, dopamine drugs bind directly to the pituitary cells.
 
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bobbler said:
Maybe @SNT Gatchaman can point if there is some new magic option/advice on whether scans can offer things today?
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If anywhere it would come from molecular imaging, which today focuses on things like neuroendocrine tumours. Perhaps imaging interrogation of focal tumours like prolactinomas might be translated to demonstrate abnormal receptor physiology. However, one problem is spatial resolution — the regions of interest are small. I think we'd probably learn more from direct biochemistry studies than imaging studies. The other problem is the above studies from the 1990s showed normal baseline prolactin, only rising abnormally with challenge. So a similar baseline imaging study might also not show anything unusual.

Here is a recent open-access review that gives an overview of pituitary molecular imaging.

Molecular imaging in pituitary neuroendocrine tumors: a narrative review of advances, challenges, and future perspectives (2026)

Molecular imaging has emerged as a promising adjunct for the evaluation of pituitary neuroendocrine tumors (PitNETs), as magnetic resonance imaging (MRI), despite being the primary imaging modality, remains inconclusive in a substantial proportion of patients. Molecular imaging techniques, including single photon emission computed tomography (SPECT) and positron emission tomography (PET), can complement anatomical MR imaging by enabling in vivo visualization of tumor metabolism, receptor expression, and amino acid transport.

This narrative review summarizes current evidence on the clinical utility of molecular imaging across corticotroph, somatotroph, lactotroph, and nonfunctioning PitNETs, with a focus on diagnostic performance and impact on patient management. Among available tracers, amino acid PET shows the most consistent added diagnostic value in patients with inconclusive MRI findings, particularly when integrated into hybrid or coregistered PET-MRI protocols.

Emerging data indicate that this approach improves tumor localization and supports clinical decision-making, including surgical planning and management of persistent or recurrent disease. Defining the precise role of molecular imaging within endocrine diagnostic pathways will require larger-scale prospective clinical trials using standardized acquisition and interpretation protocols.

Broader clinical implementation is further supported by emerging European interdisciplinary collaborations between experts in endocrinology, nuclear medicine, radiology, neurosurgery, and radiotherapy, with a shared focus on advancing individualized PitNET care.

Web | PDF | European Journal of Endocrinology | Open Access

PitNETs are known for overexpressing somatostatin receptors (SSTR) and dopamine receptors, as reflected by the use of somatostatin analog (SSA) and dopamine agonists (DA) therapy. Consequently, several studies have evaluated membrane-bound receptor-based imaging in PitNET using SSTR- or dopamine D2/D3 receptor-targeting tracers. More recently, exploratory studies have also evaluated other membrane-bound tracers targeting corticotroph-releasing hormone receptor 1 (CRH-R1), C-X-C chemokine receptor 4 (CXCR4), and vasopressin V1b receptors.
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hotblack said:
Could an imbalance of the short and long forms of prolactin receptors mean that some cells are going into apoptosis or be otherwise misbehaving in some way? Perhaps they’re responding badly to perfectly normal signals?

Could the increase that we see in response to Buspirone be a result of the body over compensating to this and trying to get a signal to somewhere and it's just not being heard so it shouts louder? Maybe some subset of cells up or down regulating in response to this imbalance of receptors elsewhere?
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On my ‘what data can we reuse’ chain if thought at the moment we may be able to ask this question of existing data.

One of the papers I was looking at determined the balance of long versus short form receptors using bulk-rna-seq. If a receptor becomes long or short form seems to be controlled by alternative splicing and dependent upon an exon (exon 10) being present in the pre-mrna. The study I am looking at used bulk rna-seq, so if we can find a good rna-seq dataset of pbmcs (or b, t or nk cells) from me/cfs patients and controls maybe we can look at this?

Anyone know of any suitable datasets? I think the pipeline for looking at this would be beyond my little Pi and require something a bit more beefy RAM wise though.

Edit: This is single cell rather than bulk but has data available and maybe relevant?
J

Thread 'Single-cell transcriptomics of the immune system in ME/CFS at baseline and following symptom provocation, 2022, Ahmed, Hanson et al.'

Now published, see post #14
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Preprint
https://www.biorxiv.org/content/10.1101/2022.10.13.512091v1
https://www.biorxiv.org/content/10.1101/2022.10.13.512091v1

SUMMARY
ME/CFS is a serious and poorly understood disease. To understand immune dysregulation in ME/CFS, we used single-cell RNA-seq (scRNA-seq) to examine immune cells in cohorts of patients and controls. Post-exertional malaise (PEM), an exacerbation of symptoms following strenuous exercise, is a characteristic symptom of ME/CFS. Thus, to detect changes coincident with...
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forestglip said:
Once they saw two studies finding increased prolactin response to a specific serotonin agonist (d-fenfluramine), they had their answer.
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I think the Sharpe 1996 (Cowen group) study had a pretty good view on the problem saying it was likely the dopamine instead of serotonin pathway that was abnormal. They wrote:
Our data question whether the enhancement of buspirone-induced prolactin release in CFS is a consequence of increased sensitivity of post-synaptic 5-HT,, receptors. It is possible that the increased prolactin response to buspirone in CFS could reflect changes in dopamine function.
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Increased prolactin response to buspirone in chronic fatigue syndrome - PubMed

My guess is that buspirone was seen as a 'dirty' drug so it's not clear what pathways it affects which complicates interpretation of the results. Prolactin has a lot of variability and confounders (sex, menstruation phase, stress, time of day, medication, etc) and changes in responses with normal baseline values are hard to interpret and see something meaningful in.

I think the genetic data pointing to the brain and the lack of other replicable ME/CFS results in the past 30 years, might explain why we see these findings as more interesting than researchers at the time.
 
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