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More Accurate Conversion of Average Blood Glucose to Hemoglobin A1c

Dr. Norris

What is Hemoglobin A1c? Hemoglobin A1c (HbA1c) is a blood test that measures the amount of glucose that is attached to a persons hemoglobin — the oxygen carrying protein found in red blood cells. The higher a person’s blood sugar, the more glucose that becomes attached. Because red blood cells last about 90 days, the HbA1c value reflects a person’s average blood glucose over the past 3 months. A HbA1c value over 6.4% indicates that a person has diabetes. For persons with diabetes, higher blood glucoses increase the risk of long term complications. Higher HbA1c levels are associated with increased rates of complications including diabetic eye disease, kidney disease, and neuropathy. For this reason, the American Diabetes Association recommends that most persons with diabetes have a goal of maintaining their HbA1c at less than 7%.

What is average blood glucose? In the past, HbA1c was the only widely available method to assess a person’s recent average blood glucose levels. Fortunately, technological advances over the past decades have enabled frequent testing of blood glucose using portable meters and even more powerfully using continuous glucose monitors (CGMs). CGMs are wearable devices that measure a persons approximate blood glucose every few minutes. Modern glucose meters and CGMs can report a user’s recent average blood glucoses.

Converting between average blood glucose and HbA1c A common question asked by persons with diabetes is what HbA1c is predicted by their recent average blood glucose. There are multiple online conversion calculators that address this question, allowing the user to enter an average glucose for which a predicted HbA1c is returned. However, two scientists at the University of Iowa recently identified and reported a small mathematical error in the equations commonly used by online calculators to predict HbA1c from recent average blood glucose. As a result, the erroneous online calculators do not provide optimal predictions. The two scientists were Dr. Joseph Lang from the Department of Statistics and Actuarial Science and Dr. Andrew Norris from our Division. The two then derived new equations that correct the error. Their findings and new equations have been peer reviewed and now are published as a letter in the prominent journal Diabetes Care (link to article).  Dr Norris would like to thank Dr Lang for uncovering the error and devising the approach for its correction. The hope is that the improved equations will be adopted by online calculators. In the meantime, on a positive note, many continuous glucose monitors report an estimated HbA1c that is termed “GMI” (“glucose management indicator”) and the equations used for GMI are typically correct. Drs. Norris and Lang’s letter also comments on a recently published perspective that highlights ongoing issues in the interconversion of recent average blood glucose to HbA1c. It is important to understand that neither HbA1c nor meter/monitor derived average blood glucose are perfectly accurate. Unsurprisingly, interconversions between these two measurements often do not agree. The revised equations of Dr Lang and Dr Norris will help the situation to some degree but perfect agreement is not possible in real life. Additional data and understanding of the variances that impact the relationship between these two measurements are needed.

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Announcing New Faculty: Gabriel Castano, MD

Dr. Castano

We are pleased to announce that Dr. Gabriel Castano is starting as a new pediatric endocrinologist in our division. He received his Medical Doctorate from the Santos School of Medicine in Monterrey, completed pediatric residency at the University of Texas Health Science Center San Antonio, and just completed the highly regarded fellowship in pediatric endocrinology at Texas Children’s Hospital / Baylor College of Medicine in Houston. He has published expertise in several areas of pediatric endocrinology, including diabetes. His ongoing clinical interests include diabetes, type 2 diabetes prevention, and bone health. In clinic, his initial practice will include general pediatric endocrinology and diabetes, as well as outreach services in Bettendorf. Welcome Dr. Castano!

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Better Understanding of an Uncommon Form of Turner Syndrome

Dr. Catherina Pinnaro

Turner syndrome is a genetic condition cause by complete or partial loss of an X chromosome in a person who otherwise would have an XX karyotype. There are multiple ways in which the X chromosome can be missing or partially lost. Sometimes, a person with Turner syndrome will have a mixture of cells in their body. An uncommon form of Turner syndrome occurs when some cells are have only one X chromosome (45,X karyotype) and other cells have three X chromosomes – termed 45,X/47,XXX mosaicism. The health implications of this form of Turner syndrome have not been well studied until now. A group of Turner syndrome experts across the United States, including our own Dr. Pinnaro, have cooperated to combine their experiences. Their findings are now published in the American Journal of Medical Genetics (PubMed link). They found that features of this form of Turner syndrome could be more subtle than more common forms. Because Turner syndrome can cause a wide variety of rare but serious health concerns, it is important for persons with Turner syndrome to receive medical care in a specialized clinic, such as the one staffed at our center by Dr. Pinnaro and Dr. Alexandrou.

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Announcing New Pediatric Endocrine Fellow: Dr. Power

Dr. Power

Today we are thrilled to announce that Dr. Gregory Power has joined our division as a new pediatric endocrine fellow. He will serve three years in this role, after which he will be a full-fledged, board-eligible pediatric endocrinologist. Dr. Power received his Medical Doctorate degree from the University of Iowa having completed undergraduate studies at Iowa State University. He just completed a three-year pediatric residency at the Riley Hospital for Children, Indiana University. While a resident he demonstrated an outstanding aptitude for and interest in pediatric endocrinology. In 2021, he was selected to join the PedsENDO Discovery Program administered by the Pediatric Endocrine Society. He graduated medical on the Research Distinction Tract, studying lung disease in premature infants. A warm welcome to Dr. Power!!

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Dr. Curtis Promoted to Full Professor

Dr. Curtis

Please join me in congratulating Dr. Vanessa Curtis for her well earned promotion to full professor!! In brief, Dr. Curtis has been promoted in recognition of her clinical mastery and leadership, her teaching leadership, her skills in clinical communication, and her nationally recognized scholarship in several aspects of pediatric endocrinology. She joined the University of Iowa Hospitals and Clinics in 2011, having just completed a pediatric endocrine fellowship at the University of Wisconsin. Since that time, she has become a nationally recognized clinical expert as regards the endocrinology of young athletes. Additionally, she built the leading state/regional clinic for obese youth. We are especially thankful for her leadership as the Director of our Division’s pediatric endocrinology fellowship program, ushering it into its most successful era. To boot, she is an outstanding physician and superb teacher. Earlier this year she was tapped to become the Director of the Child and Community Health Division, highlighting her leadership skills. Once again, congratulations Dr. Curtis!

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Dr. Parra Villasmil Completes Pediatric Endocrine Fellowship

Dr. Parra Villasmil

We are extremely proud of Dr. Graciela Parra Villasmil. For the past 3 years, Dr. Parra Villasmil has been a pediatric endocrinology fellow in our program. Today she finishes this training and will officially become a “board eligible” pediatric endocrinologist. During these past three years, Dr. Parra Villasmil has been an exemplary fellow, delivering excellent clinical care and demonstrating exceptional clinical leadership. Her contributions include being an enthusiastic volunteer at Diabetes Camp Hertko Hollow. While a fellow, she has been a very energetic scholar, publishing several times, including a case report regarding the co-occurrence of hyperglycemic hyperosmolar state and diabetic ketoacidosis. She presented a roundtable lecture at the 2023 North American Society for Pediatric and Adolescent Gynecology meeting and a poster at the 2023 Pediatric Endocrine Society meeting. She has been named a 2023-2025 Collaborative Alliance for Pancreatic Education and Research (CAPER) scholar, and received an annual top research project award from CAPER. Several other of her awards received as a fellow have been previously mentioned in this blog. Dr. Parra Villasmil will be taking a position at Blank Children’s Hospital in Des Moines, joining their Pediatric Endocrine team. Her enthusiasm, patient care skills, and positive energy will be missed by our division. Congratulations Dr. Parra Villasmil!

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Dr. Pinnaro Recognized for her Outstanding Teaching

Dr. Catherina Pinnaro

On May 31st, Dr. Pinnaro received the Excellence in Clinical Coaching award from the Graduate Medical Education office. This award is given to faculty who are distinguished as outstanding clinical teachers of resident and fellow physicians. Comments written about Dr. Pinnaro’s teaching include a reflection of her approach to hospital rounds where she is renowned for “probing each learner with thought-provoking questions to assess their understanding, empowering the learners to take ownership of the patients, and dropping clinical pearls about even the mundane patient.” Congratulations Dr. Pinnaro, and thank you for your outstanding clinical teaching efforts.

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Drs. Curtis and Pinnaro Provide Invited Commentary on Pubertal Timing

A variety of pathological processes can induce puberty earlier than otherwise would normally occur. When a child enters puberty, an important question is whether the timing is abnormally early. Pediatric endocrinologists are often the arbitrators of this question. Data defining the normal ages of puberty start are thus important. Data suggest that normal timing varies depending on a child’s genetics and environment. A recent publication in JAMA Network Open reports data collected from over 100,000 youth with Asian American, Native Hawaiian, and/or Pacific Islander heritage (link to article). To help interpret the findings, Drs. Vanessa Curtis and Catherina Pinnaro from our division were asked to provide their commentary on the article. Their commentary can be found here (link, which has link to the open source full text). They conclude that “[the] study […] emphasizes the necessity for precision and the pitfalls encountered when using race and ethnicity as a proxy for genetic background.”

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JDRF Diabetes Fundraising Walk

The JDRF is a philanthropic, nonprofit organization that raises funds to support research aimed at curing, preventing, and better treating type 1 diabetes. On Saturday, May 11, the JDRF held its annual fundraising walk in Cedar Rapids. Our Division, led by Drs. Pinnaro and Alexandrou, organized a team of walkers to help the cause. Walkers from our division on the team included Drs. Alexandrou and Pinnaro, nurse practitioner Alex, diabetes nurses Haylee and Sue, pharmacist Lisa, our administrator Teresa, and research coordinator Emma, as well as spouses, kids, and a few of our dogs! As an unexpected perk, team members got to meet Iowa basketball star forward Hannah Stuelke (pictured below with nurse Sue and Dr. Alexandrou).

L->R: diabetes nurse Sue, Iowa basketball star Hannah Stuelke, Dr. Alexandrou.
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A Newly Identified Mechanism of Obesity-Induced Pituitary Dysfunction Contributes to Metabolic Dysfunction Associated Fatty Liver Disease

Dr. Norris

Obesity impairs various aspects of pituitary function. Perturbations in the thyroid, growth hormone, gonadal, and adrenal axes are well documented. However, the mechanisms involved are not well understood. Furthermore, it is possible that the pituitary dysfunction induced by obesity might contribute to the medical complications of obesity. Dr. Norris, from our division, recently assisted with new research that begins to address these knowledge gaps. The investigators found that obesity in mice impaired the ability of pituitary cells to activate their cellular unfolded protein response (UPR). The UPR is a mechanism that helps protect cells against various stressors. Importantly, when the UPR was disrupted in pituitary cells by genetic manipulation, pituitary dysfunction similar to that in obesity resulted, especially in the thyroid axis. Furthermore, primary genetic UPR disruption in the pituitary resulted in UPR disruption in the liver in a manner that could contribute to fatty liver disease. The work will be published in Cell Metabolism and its abstract is available on PubMed (link). The work was conducted in the lab of Dr. Ling Yang in the F.O.E. Diabetes Research Center at the University of Iowa.