How IGF-1 LR3 Affects Fasting Insulin

IGF-1 LR3 lowers fasting insulin acutely but worsens insulin sensitivity chronically:

1. Pancreatic suppression: IGF-1 has insulin-like activity, so when free IGF-1 is high the pancreas reduces insulin secretion. In a human infusion study, IGF-1 dropped fasting insulin by 57%, from 16.7 to 7.2 mU/L (Russell-Jones et al., 1997).
2. The HOMA-IR artefact: HOMA-IR is calculated from fasting glucose and fasting insulin. With insulin suppressed and glucose drawn down, HOMA-IR on cycle looks excellent, but it reflects switched-off insulin output, not improved receptor sensitivity.
3. Chronic insulin resistance: sustained supraphysiological IGF-1 desensitises insulin signalling over time. In acromegaly, HOMA-IR correlates with IGF-1 at r=0.83 and more than half of patients have abnormal glucose at diagnosis (Mori et al., 2013; Stelmachowska-Banas et al., 2009).
4. Biphasic trajectory: an early apparent improvement (low insulin, low glucose) that masks a later compensatory hyperinsulinaemic, insulin-resistant state.

Acute / early cycle (deceptive):

• Fasting insulin falls, potentially by half, because IGF-1 suppresses secretion
• HOMA-IR drops and looks great. This is an artefact, not a sensitivity gain.

Worked HOMA-IR example (HOMA-IR = glucose mmol/L x insulin mU/L / 22.5):

• Baseline: 5.0 x 8 / 22.5 = 1.78 (normal)
• On cycle, insulin suppressed: 4.2 x 4 / 22.5 = 0.75 (artefactually low)
• Chronic supraphysiological (acromegaly pattern): 6.5 x 20 / 22.5 = 5.78 (insulin resistant)

Reference: HOMA-IR above about 2.8-2.9 indicates insulin resistance (Schrank et al., 2024). The chronic figure above is clearly pathological.

The monitoring trap: a fasting insulin or HOMA-IR drawn during active LR3 use will give a falsely reassuring number. It is not interpretable on cycle.

Baseline: fasting insulin and fasting glucose before starting, calculate HOMA-IR, ideally drawn the same morning.

The key timing rule: do not draw insulin or HOMA-IR while LR3 is active. Come off the compound for at least 48 to 72 hours before the blood draw, or the suppressed insulin makes the result meaningless.

During use: track HOMA-IR at baseline, mid-cycle (off LR3 48-72h), and post-cycle. A rising trend across properly-timed draws is the real insulin-resistance signal.

Lab consistency: fasting insulin assays vary between labs; use the same one across the protocol.

Interpret HOMA-IR only off cycle: this is the single most important point. An on-cycle HOMA-IR of 0.8 does not mean you are metabolically healthy, it means IGF-1 switched off your pancreas.

Watch the chronic direction: if properly-timed HOMA-IR climbs above ~2.9, insulin resistance is developing. Reassess dose and consider stopping.

Do not stack into a metabolic mess: running LR3 with exogenous insulin, GH, or MK-677 compounds the glucose and insulin disruption and makes every reading harder to interpret.

Support sensitivity: dietary carbohydrate management, zone 2 cardio, and (with physician input) metformin or berberine are the evidence-based levers if HOMA-IR trends up.