Serum Insulin-Like Growth Factor-1 (IGF-1) Age-Specific Reference Values for Healthy Adult Population of Serbia

Challenges of insulin-like growth factor-1 testing

Insulin-like growth factor 1 (IGF-1), primarily synthesized in the liver, was initially discovered due to its capacity to replicate the metabolic effects of insulin. Subsequently, it emerged as a key regulator of the actions of growth hormone (GH), managing critical processes like cell proliferation, differentiation, and apoptosis. Notably, IGF-1 displays a longer half-life compared to GH, making it less susceptible to factors that may affect GH concentrations. Consequently, the measurement of IGF-1 proves to be more specific and sensitive when diagnosing conditions such as acromegaly or GH deficiency. The recognition of the existence of IGFBPs and their potential to interfere with IGF-1 immunoassays urged the implementation of various techniques to moderate this issue and provide accurate IGF-1 results. Additionally, in response to the limitations associated with IGF-1 immunoassays and the occurrence of discordant IGF-1 results, modern mass spectrometric methods were developed to facilitate the quantification of IGF-1 levels. Taking advantage of their ability to minimize the interference caused by IGF-1 variants, mass spectrometric methods offer the capacity to deliver robust, reliable, and accurate IGF-1 results, relying on the precision of mass measurements. This also enables the potential detection of pathogenic mutations through protein sequence analysis. However, despite the analytical challenges, the discordance in IGF-1 reference intervals can be attributed to a multitude of factors, potentially leading to distinct interpretations of results. The establishment of reference intervals for each assay is a demanding task, and it requires nationwide multicenter collaboration among laboratorians, clinicians, and assay manufacturers to achieve this common goal in a cost-effective and resource-efficient manner. In this comprehensive review, we examine the challenges associated with the standardization of IGF-1 measurement methods, the minimization of pre-analytical factors, and the harmonization of reference intervals. Particular emphasis will be placed on the development of IGF-1 measurement techniques using "top-down" or "bottom-up" mass spectrometric methods.

A Case Report of Sheehan Syndrome: A Rare Cause of Hypopituitarism

Sheehan syndrome is a rare cause of hypopituitarism characterized by pituitary gland necrosis after postpartum hemorrhage. It is a pertinent cause of maternal morbidity and mortality in developing countries with deficient obstetrical care but is frequently overlooked in developed countries where its occurrence is uncommon. We present the case of a 66-year-old female diagnosed with Sheehan syndrome more than 30 years after her last delivery complicated by postpartum hemorrhage. Although the patient presented several symptoms and signs of pituitary hormonal deficiencies, a diagnosis had never been established before. The complete laboratory analysis revealed a deficiency in the pituitary axis, and the cranial imaging showed an empty sella turcica. Hormonal replacement therapy resolved several impairments in terms of general energy, physical capacity, temperature regulation, skin characteristics, and sexual function. It also improved her cardiovascular and osteoporosis risk, and, most importantly, prevented a potential life-threatening adrenal crisis. This report highlights the subtle manifestations of Sheehan syndrome to help clinicians establish a prompt diagnosis. Even in developed countries such as Portugal, this condition should be regarded as a potential cause of hypopituitarism.

Proposed reference intervals of serum insulin-like growth factor-1 (IGF-1) levels in older Japanese populations

Measurements of serum insulin-like growth factor 1 (IGF-1) levels are useful surrogate markers for the diagnosis and management of patients with growth hormone-related disorders. We have previously published normative data of serum IGF-1 levels for the Japanese population aged 0-77 years by combining and analyzing previously reported references, which were separately and independently constructed, to properly reflect data in the transition period. Although the reference is widely used in both clinical and research settings, the reference did not include data for those aged >77 years, raising the question of how we would evaluate patients over those ages. In this study, we extended the age- and sex-specific reference ranges of serum IGF-1 levels to the age of 80 years by reanalyzing combined data on serum IGF-1 levels from previously published references. Based on our results, we proposed that individuals aged >80 years can be evaluated using the references set at the age of 80 years. However, our proposal was based on a very limited number of participants. Therefore, physicians should exercise caution when interpreting IGF-1 standard deviation scores for those aged >80 years because they are not exactly correct but acceptable.