# Hypothalamic amenorrhea

> Hormone Consultants on amenorrhea and LH pulses — Hormone Consultants examines kisspeptin experiments in hypothalamic amenorrhea: restored LH pulses, fading responses and the surrounding physiology.

The reply changed as the experiment continued. That makes timing essential to the question of capacity.

## The infusion experiment

In [five women with hypothalamic amenorrhea, continuous intravenous kisspeptin-54 restored pulsatile LH secretion](https://pubmed.ncbi.nlm.nih.gov/24517142/). LH pulses rose from 1.6 to 5.0 per 8 h versus vehicle, while pulse secretory mass rose from 3.92 to 23.44 IU/L. Those are different descriptions of the response: how often secretion occurred and the secretory mass of a pulse.

The same experiment contains a complication I consider central. [The highest infusion rate produced tachyphylaxis during the infusion](https://pubmed.ncbi.nlm.nih.gov/24517142/): a rapidly weakening response to continued stimulation. An account that stops at the restored pulses loses the observation that makes the experiment so instructive.

Restored activity deserves admiration. My curiosity gathers around the fading reply. The system’s capacity was being tested over time, with stimulation itself capable of changing the answer.

![Two horizontal bars compare 1.6 LH pulses with vehicle and 5.0 with kisspeptin-54 per 8 h in five women with hypothalamic amenorrhea.](images/lh-pulses.svg)

*LH pulse counts in the [five-woman infusion study](https://pubmed.ncbi.nlm.nih.gov/24517142/); the highest infusion rate also produced tachyphylaxis.*

## Repeated exposure

An earlier study followed a longer sequence. Women with hypothalamic amenorrhea received repeated subcutaneous kisspeptin-54 over 14 days. [The mean LH increment was 24.0 ± 3.5 IU/L within 4 h on day 1, falling to 2.5 ± 2.2 IU/L on day 14](https://pubmed.ncbi.nlm.nih.gov/19820030/). The initial response and the later response tell strikingly different stories within that research protocol.

There is a temptation to treat the first response as a demonstration of what a substance does, then file the subsequent loss under limitations. I think that gets the emphasis backwards. The change in responsiveness is a finding about the system, and deserves the same status as the initial stimulation.

A [review of KISS1R pharmacology describes desensitization, internalization and recycling of resensitized receptors](https://pubmed.ncbi.nlm.nih.gov/25765628/) as processes governing sustained or attenuated signaling. That helps explain why the pattern of exposure matters. It supplies no personal regimen. Inventing one from these experiments would misuse what they measured.

![Illustrated gloved hands aligning capped sample tubes in a long rack on a laboratory worktop.](images/serial-sampling.webp)

*An invented assay-room scene about a series of measurements, rather than a single impressive result.*

## The surrounding physiology

The hormone system in these studies has a context. A [review of functional hypothalamic amenorrhea describes suppression of GnRH pulsatility with psychological stress, disordered eating, low body weight and excessive exercise](https://pubmed.ncbi.nlm.nih.gov/33345352/), and identifies kisspeptin-containing KNDy neurons as central to that regulation. These factors are discussed in the review; they are not a description of every participant in the infusion experiment.

That context adds to my demands on a successful challenge. Showing that activity can be provoked leaves the conditions around that activity to be understood. For this site, the interesting consultation is still with the physiology: what capacity was present, under which circumstances, and how did it change?

The next essay follows a response into a different kind of endpoint: [food intake after LH stimulation](/appetite).

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Hormone Consultants houses my questions for published research, with no consulting business behind the name and no medical advice in these essays.