PMC9684460_01
Symptoms of cyclic vomiting and intractable hypoglycaemia in this T1D patient. (A) Date of vomiting onset and the first day of menstruation. (B, C) Continuous blood glucose monitoring after the remission of vomiting (B) and before discharge (C) during one hospital stay by Abbott Freestyle Libre Flash Glucose Monitoring System. TIR, time in range. TBR, time below range. TAR, time above range. (D) Body weight and HbA1c levels after suffering from hypoglycaemia. (E) Blood glucose and serum insulin levels during overnight fasting and refeeding monitoring.
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The onset of vomiting seemed to be associated with menstruation ( Figure 1A ), but attempts to create artificial menstrual cycles to prevent abdominal pain by taking oral contraceptives were failed and the levels of sexual hormones were in normal ranges during her menstrual cycle. After that, the patient started to experience fluctuating blood glucose with severe hypoglycaemia ( Figure 1B ), despite tight control of continuous subcutaneous insulin glulisine infusion (0.5U/h, 8-10; 0.25U/h, 10-12; 0.1U/h, 12-15; 0.05U/h, 15-24; 0.05U/h, 5-7) via smart insulin pump (Medtronic, Models MMT-712). 3-4 days later, the patient returned to basal condition without hypoglycaemia and was subsequently discharged ( Figure 1C ). The patient started to have severe hypoglycaemia in July of 2017, after that her HbA1c levels decreased from 10.9% to 5.9% ( Figure 1D ) and her body weight increased rapidly from 60.1 to 97.6kg ( Figure 1D ) and she developed obesity with a body mass index (BMI) of 31.7kg/m2. A delayed fasting hypoglycaemia of 2.80mM blood glucose happened at 2:00am on the next early morning, which was followed with a slow elevation of blood glucose to 14.19mM before breakfast at 7:00am ( Figure 1E ). After breakfast, the blood glucose rapidly decreased to 3.66mM at 10:00am, which was then followed with a reactive hyperglycaemia of 12.12mM blood glucose at 11:00am ( Figure 1E ). A positive response to glucagon stimulation at the time of hypoglycaemia is indicative of insulin-mediated hypoglycaemia ( Figure S1 ). Unexpectedly, both free and bound insulin levels simultaneously fluctuated with blood glucose in this patient ( Figure 1E ). Considering the injected fast-acting insulin was not degraded quickly, but recycled in the blood of the patient ( Figures 1E ,  2A ), the half-life of the exogenous insulin must be prolonged by the effects of IAs.
Fluctuation of blood glucose and serum insulin levels in oral glucose tolerance test and insulin withdraw study. (A) Oral glucose tolerance test was performed in this patient by oral ingestion of 75g of glucose preceded by an overnight fast and levels of blood glucose and serum insulin were measured at 0, 1, 2, 3, and 4h after glucose ingestion. Levels of free and total insulin were measured using the methods as described in 
Figure S2
. Bound insulin was calculated by subtracting free insulin from total insulin. (B) After careful depletion of subcutaneous insulin, the patient was stabilized on intravenous insulin which was then discontinued. Blood glucose and serum insulin were monitored in the following time until the patient had sustained extreme hyperglycaemia, the sign of exhausted injected insulin. Total insulin was measured using the method as described in 
Figure S2
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Table 1 ), we speculated that the spontaneous hypoglycaemia in our patient was possibly caused by dysfunctions of injected insulin due to the presence of IAs. To test this hypothesis, both free and bound insulin levels were serially measured in the patient using methods developed and validated in house ( Figure S2 ). To further confirm this finding, we measured the patient's insulin levels during an oral glucose tolerance test and found both the free and bound insulin levels also fluctuated along with the blood glucose levels ( Figure 2A ). Considering the injected fast-acting insulin was not degraded quickly, but recycled in the blood of the patient ( Figures 1E ,  2A ), the half-life of the exogenous insulin must be prolonged by the effects of IAs. Serial determinations of total insulin suggested that the circulating insulin had a prolonged serum half-time of 25h ( Figure 2B ).