The Influence of Branched-Chain Amino Acid Supplementation on Fatigue and Tryptophan Metabolism After Acute and Chronic Exercise in Older Adults: Protocol for a Pilot Randomized Controlled Trial

BACKGROUND

Fatigue is a strong predictor of negative health outcomes in older adults. Kynurenine, a metabolite of tryptophan, is strongly associated with fatigue. Reductions in fatigue are observed with exercise; however, exercise training does not completely alleviate symptoms. Branched-chain amino acids (BCAAs) have been shown to have advantageous effects on exercise performance and compete with kynurenine for transport into the central nervous system. Thus, the combination of BCAA and exercise may exert synergized effects of mental and physical fatigue. Therefore, we hypothesize that BCAA added to exercise will shift kynurenine metabolism toward enhanced synthesis of kynurenic acid, thereby reducing fatigue.

OBJECTIVE

This randomized, double-blind, placebo-controlled trial aims to compare the effects of acute (approximately 45 min) and chronic (8 wk) exercise with and without BCAA supplementation on mental and physical fatigue and assess whether the hypothesized outcomes are modulated by changes in kynurenine metabolism in 30 older adults (n=15, 50% per group).

METHODS

Older adults (aged 60-80 y) who do not exercise >2 days per week and self-report fatigue (≥3 on a scale of 1-10) will be recruited. Participants will be randomized to either the exercise+BCAA group or exercise+placebo group. Participants will engage in high-volume, moderate-intensity, whole-body exercise training (aerobic and resistance exercise; either in-person or web-based sessions) 3 times per week for 8 weeks. In addition, participants will consume daily either 100 mg/kg body weight of BCAA (2:1:1 leucine:isoleucine:valine) or placebo (maltodextrin) throughout the 8-week intervention. BCAA and placebo powders will be identical in color and dissolved in 400 mL of water and 2.5 g of a calorie-free water flavor enhancer. Muscle biopsies will be collected before and after the intervention after a 12-hour fast to examine changes in the biomarkers of tryptophan metabolism and inflammation. Our primary outcomes include changes in mental and physical fatigue and metabolism after the 8-week exercise training between the 2 groups. Mental and physical fatigue will be measured before and after the intervention. Mental fatigue will be subjectively assessed through the completion of validated questionnaires. Physical fatigue will be measured by isometric handgrip, 1-repetition maximum, chair rise, 400-meter walk, and cardiopulmonary exercise tests.

RESULTS

The study was funded in March 2022, with an anticipated projected data collection period lasting from January 2023 through December 2023.

CONCLUSIONS

The discovery that kynurenine concentrations are associated with fatigue and are responsive to BCAA supplementation during exercise training could have important implications for the development of future interventions, both lifestyle and pharmacologic, to treat fatigue in older adults.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05484661; https://www.clinicaltrials.gov/study/NCT05484661.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/52199.

Hypercalcemia of Malignancy Complicated by Osteonecrosis of the Jaw Treated With Cinacalcet

Hypercalcemia of malignancy (HCM) is a common complication seen in patients with cancer and is associated with high morbidity and mortality. Current long-term medical therapy for HCM focuses on inhibiting bone resorption with bisphosphonates or denosumab, which have the rare complication of osteonecrosis of the jaw. This case illustrates cinacalcet as an effective therapy for severe HCM resulting from PTH-related peptide in the setting of osteonecrosis of the jaw. Although the mechanism of action remains unclear, cinacalcet has been successful in other HCM cases even if not associated with elevated PTH-related peptide.

CLINICAL TRIAL OF METFORMIN FOR FRAILTY PREVENTION IN COMMUNITY-DWELLING OLDER ADULTS WITH PRE-DIABETES

Background

Metformin may reduce frailty through improving insulin resistance and inflammation, aging mechanisms known to increase frailty risk. We describe a randomized clinical trial of metformin for frailty prevention in community-dwelling older adults with pre-diabetes and provide baseline characteristics of randomized participants.

Methods

Older adults (65+ years) are studied in this randomized, double-blind, placebo-controlled trial of metformin (max 2,000 mg/day). Pre-diabetes, required for inclusion, is assessed by 2-hour oral glucose tolerance test (OGTT). Individuals with glomerular filtration rate < 45 mL/min and frail individuals (Fried criteria) are excluded. The primary outcome, frailty, is assessed by both Fried criteria and frailty index. Secondary outcomes are physical function (short physical performance battery), lower extremity strength (Biodex), 6-minute walk, inflammation (systemic and skeletal muscle tissue), muscle insulin signaling, insulin sensitivity (insulin clamp), glucose tolerance (OGTT), and body composition (dual-energy x-ray absorptiometry). Subjects are followed for 2 years with safety assessments every 3 months and frailty assessment and OGTT every 6 months.

Results

145 participants (49% female, 35% Hispanic) are randomized. Mean age is 71.8 ± 5.4 years (range: 65-88), body mass index is 30.8 ±6 kg/m2, and Hemoglobin A1c is 5.6 ±0.4%. Using Fried criteria, 63.4% have frailty score of 0, 30.3% a score of 1, and 6.2% a score of 2.

Conclusion

Metformin is being examined as a potential therapeutic agent to prevent frailty in older adults with pre-diabetes. Findings from this trial may have future implications for screening and treatment of pre-diabetes in older adults for the prevention of frailty.

INCLUSION OF ETHNICALLY DIVERSE POPULATIONS IN CLINICAL TRIALS OF HEALTHSPAN: IMPLICATIONS FROM THE SALSA STUDY

Background

Geroscience-guided clinical trials focused on healthspan may seek to enroll older adults initially free of chronic diseases and disability. Here we examine healthspan in the San Antonio Longitudinal Study of Aging (SALSA), a cohort of 749 community-dwelling older (65+ years) Mexican Americans (MA) and European Americans (EA), and describe prevalence and characteristics associated with poor healthspan.

Methods

Poor healthspan was defined at the SALSA baseline exam as presence of any one of: 1) chronic disease (diabetes, myocardial infarction, congestive heart failure, stroke, chronic obstructive pulmonary disease, or cancer); 2) dependence in basic or instrumental activities of daily living; or 3) mini mental state exam score < 18. Frailty was defined by Fried phenotype criteria. The association of poor healthspan with age, sex, ethnic group, socioeconomic status (SES), and frailty was assessed using chi-square or t-tests.

Results

544 (72.6%) participants met criteria for poor healthspan, which was associated with older age (69.6 ±3.4 vs. 69.3 ±3.4, p< 0.05), male sex (77.3% vs. 69.2%, p< 0.05), MA ethnicity (77.4% vs. 67.3%, p< 0.05), lower income (11.3 ±3.1 vs. 12.2 ±2.9, p< 0.001 and education (10.4 ±4.6 vs. 12.7 ±3.2, < 0.0001), and frailty (95.5% vs. 4.6%, p< 0.001).

Conclusion

Poor healthspan was highly prevalent (>70%) in SALSA and associated with MA ethnicity, low SES, and frailty. Geroscience-guided clinical trials of potential interventions to improve healthspan by preventing chronic diseases and disability may under-represent individuals of ethnic minority background and lower SES and, thereby, jeopardize generalizability of the findings to the broader population.

A Randomized Placebo-Controlled Trial of Metformin for Frailty Prevention in Older Adults

Frailty is a progressive physical decline leading to higher morbidity and mortality in older adults. Previous studies have demonstrated shared mechanisms between insulin resistance, inflammation, and frailty. The purpose of this trial is to determine whether metformin prevents frailty in non-frail, community-dwelling older adults (≥65 years) with pre-diabetes, determined by 2-hour oral glucose tolerance test (OGTT). Frail individuals (Fried criteria) and those with renal impairment (glomerular filtration rate &lt;45 mL/min) are excluded. Eligible participants are randomized to metformin or placebo and followed for two years. The primary outcome is frailty; secondary outcomes include physical function (short physical performance battery), systemic and skeletal muscle inflammation (plasma and muscle inflammatory markers), muscle insulin signaling (muscle biopsy), insulin sensitivity (insulin clamp), glucose tolerance (OGTT), and body composition (dual-energy x-ray absorptiometry) measurements. Participants are followed every 3 months for safety assessments, every 6 months for frailty assessment and OGTT, and every 12 months for muscle biopsy. Currently, 99 participants, including 53 (53.5%) male and 91 (91.9%) white, are active (54) or have completed the study (35). At baseline, mean age was 72.3 ± 5.5 years, body mass index was 30.7 ± 5.9 kg/m2, and Hemoglobin A1c was 5.73 ± 0.37%. Mean frailty score was 0.5 ± 0.6 and the proportion of non-frail and pre-frail participants were 58.6% (n = 58) and 41.5% (n = 41), respectively. Findings of this clinical trial may have future implications for the use of metformin in older adults with pre-diabetes in order to prevent the onset of frailty.

Abnormal body composition in patients with adrenal adenomas

OBJECTIVE

Increased visceral fat and sarcopenia are cardiovascular risk factors that may explain increased cardiovascular morbidity and frailty in patients with adrenal adenomas. Our objective was to compare body composition measurement of patients with adrenal adenomas to referent subjects without adrenal disease.

DESIGN

Cross-sectional study, 2014-2018.

METHODS

Participants were adults with nonfunctioning adrenal tumor (NFAT), mild autonomous cortisol secretion (MACS), and Cushing syndrome (CS) and age, sex, and BMI 1:1 matched referent subjects without adrenal disorders. Main outcome measures were body composition measurements calculated from abdominal CT imaging. Intra-abdominal adipose tissue and muscle mass measurements were performed at the third lumbar spine level.

RESULTS

Of 227 patients with adrenal adenomas, 20 were diagnosed with CS, 76 with MACS, and 131 with NFAT. Median age was 56 years (range: 18-89), and 67% were women. When compared to referent subjects, patients with CS, MACS, and NFAT demonstrated a higher visceral fat (odds ratio (OR): 2.2 (95% CI: 0.9-6.5), 2.0 (1.3-3.2), and 1.8 (1.2-2.7) and a lower skeletal muscle area (OR: 0.01 (95% CI: 0-0.09), 0.31 (0.18-0.49), and 0.3 (1.2-2.7)) respectively. For every 1 µg/dL cortisol increase after overnight dexamethasone, visceral fat/muscle area ratio increased by 2.3 (P = 0.02) and mean total skeletal muscle area decreased by 2.2 cm2 (P = 0.03).

CONCLUSION

Patients with adrenal adenomas demonstrate a lower muscle mass and a higher proportion of visceral fat when compared to referent subjects, including patients with NFAT. Even a subtle abnormality in cortisol secretion may impact health of patients with adenomas.

Baseline Characteristics of Participants in a Randomized Controlled Trial of Metformin for Frailty Prevention

We are conducting a double-blind, randomized controlled trial of metformin for frailty prevention. Participants are adults aged 65+ years with pre-diabetes assessed by 2-hour oral glucose tolerance test (OGTT). Those who are frail (Fried criteria) are excluded. Participants are randomized to metformin (maximum dose of 2,000 mg/day) vs. placebo and followed for 2 years. The primary outcome is frailty (category and score); secondary outcomes are physical performance and function (short physical performance battery, 6-minute walk, lower extremity strength), systemic and skeletal muscle tissue inflammation, muscle insulin signaling, insulin sensitivity (insulin clamp), glucose tolerance (OGTT), and body composition (dual-energy x-ray absorptiometry). Safety assessments occur every 3 months; frailty, systemic inflammation, and OGTT are assessed at baseline and every 6 months, and insulin clamp with muscle biopsies are assessed at baseline and every 12 months. To date, 85 subjects have been randomized; 120 completers are planned. Mean age is 72.8 ± 5.7 years, 55.3% are male, and 43.5% were Hispanic. Mean BMI is 30.2±5.8 kg/m2, waist circumference is 104.4 ±15.5 cm, fasting glucose is 102.3 ± 10.0 mg/dL, Hemoglobin A1c is 5.8 ±0.3, and glucose at 2 hours during OGTT is 167.3 ± 17.8 mg/dL. Metformin is being examined in this study as a potential therapeutic agent to prevent frailty in older adults with pre-diabetes. Findings from this trial may have future implications for the screening and potential treatment of pre-diabetes in older patients with metformin for the prevention of frailty.

Treatment of Thyroid Dysfunction and Serum Lipids: A Systematic Review and Meta-analysis

CONTEXT

Hyperthyroidism is associated with low levels of cholesterol and triglycerides, and hypothyroidism is associated with hypercholesterolemia and hypertriglyceridemia.

OBJECTIVE

The aim of this systematic review was to investigate the impact of therapy for overt and subclinical hyper- and hypothyroidism on serum lipids.

DATA SOURCES

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and Scopus from 1970 through April 5, 2018.

STUDY SELECTION

Pairs of independent reviewers selected randomized and observational studies evaluating lipid parameters in patients undergoing treatment for hyper- or hypothyroidism.

DATA EXTRACTION

Pairs of independent reviewers extracted data and appraised studies.

DATA SYNTHESIS

Treatment of overt hyperthyroidism showed a significant increase in total cholesterol (TC) by 44.50 mg/dL (95% confidence interval [CI]: 37.99, 51.02), low-density lipoprotein cholesterol (LDL-C) by 31.13 mg/dL (95% CI: 24.33, 37.93), high-density lipoprotein cholesterol (HDL-C) by 5.52 mg/dL (95% CI: 1.48, 9.56), apolipoprotein A (Apo A) by 15.6 mg/dL (95% CI: 10.38, 20.81), apolipoprotein B (apo B) by 26.12 mg/dL (95% CI: 22.67, 29.57), and lipoprotein (Lp[a]) by 4.18 mg/dL (95% CI: 1.65, 6.71). There was no significant change in triglyceride (TG) levels. Treatment of subclinical hyperthyroidism did not change any lipid parameters significantly. Levothyroxine therapy in overt hypothyroidism showed a statistically significant decrease in TC by -58.4 mg/dL (95% CI: -64.70, -52.09), LDL-C by -41.11 mg/dL (95% CI: -46.53, -35.69), HDL-C by -4.14 mg/dL (95% CI: -5.67, -2.61), TGs by -7.25 mg/dL (95% CI: -36.63, 17.87), apo A by -12.59 mg/dL (95% CI: -17.98, -7.19), apo B by -33.96 mg/dL (95% CI: 41.14, -26.77), and Lp(a) by -5.6 mg/dL (95% CI: -9.06, -2.14). Levothyroxine therapy in subclinical hypothyroidism showed similar changes but with a smaller magnitude. The studies contained varied population characteristics, severity of thyroid dysfunction, and follow-up duration.

CONCLUSIONS

Treatment of overt but not subclinical hyperthyroidism is associated with worsening of the lipid profile. Levothyroxine therapy in both overt and subclinical hypothyroidism leads to improvement in the lipid profile, with a smaller magnitude of improvement in subclinical hypothyroidism.

Drivers of the Decision to Biopsy and Follow-Up of Small Suspicious Thyroid Nodules

OBJECTIVE

In 2015, the updated American Thyroid Association (ATA) guidelines recommended observation for suspicious subcentimeter thyroid nodules, based on their indolent course. We aimed to evaluate the frequency of biopsy in suspicious thyroid nodules since the introduction of these guidelines, including factors contributing to clinical decision-making in a tertiary care center.

METHODS

We conducted a retrospective study of patients in the Mayo Clinic, Rochester, Minnesota, with new, subcentimeter suspicious thyroid nodules (by report or by sonographic features) between March, 2015, and November, 2017, not previously biopsied.

RESULTS

We identified 141 nodules in 129 patients: mean age 58.1±14.1 years, 74% female, 87% Caucasian. The frequency of biopsy in suspicious thyroid nodules was 39%. Ultrasound features that were the strongest predictors for biopsy on multivariate analysis included: nodule volume (odds ratio [OR] 37.3 [7.5-188.7]), radiology recommendation for biopsy (OR 2.6 [1.8-3.9]) and radiology report of the nodule as "suspicious" (OR 2.1 [1.4-3.2]). Patient's age and degree of comorbidities did not change the likelihood for biopsy, nor did it vary by clinician type or how the nodule was initially found (incidentally or not incidentally). Among 86 nodules that were not biopsied, 41% had no specific follow-up recommendations.

CONCLUSION

One third of suspicious thyroid nodules underwent biopsy since the release of updated ATA guidelines. Factors driving thyroid biopsy seem to be associated with nodule characteristics but not with patient factors including age and comorbidities. Further studies and development of decision aides may be helpful in providing individualized approaches for suspicious thyroid nodules.

ABBREVIATIONS

ATA = American Thyroid Association; OR = odds ratio.

OR32-1 Endocrine Manifestations of Erdheim-Chester Disease: The Mayo Clinic Experience

Objective: Erdheim- Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis characterized by multisystem tissue infiltration of foamy histiocytes. Very few studies have investigated the prevalence of endocrine abnormalities in patients with ECD. Based on limited data, it is known that endocrine manifestations are not uncommon. The objective of this study was to characterize the extent of endocrine gland involvement and hormonal function abnormalities in the largest reported endocrine cohort of patients with ECD. Design: Retrospective chart review study of patients with ECD evaluated at the Mayo Clinic from January 1990 to June 2018. A tissue biopsy confirming the diagnosis of ECD was necessary for inclusion in this study. In all cases, the diagnosis of ECD was confirmed using clinical criteria in conjunction with histopathologic findings. Clinical, laboratory, and imaging data were collected. Results: Eighty-three patients with confirmed ECD were included in our study (71.1% women, 83.1% Caucasian, median age at time of diagnosis 55.2[46.3-66.1]). Symptom onset preceded the diagnosis by a median time of 2.7[1.0-6.9] years. Forty-eight patients (57.8%) had at least one hormonal deficiency. Central diabetes insipidus (25.3%) was the most common endocrine manifestation at initial presentation. Fifty percent of patients with central diabetes insipidus had at least one co-existent anterior pituitary deficiency at presentation, most commonly hypogonadism (40%). Among patients that had further endocrine evaluation, 16/64 (25.0%) had primary hypothyroidism and 7/64 (10.9%) had central hypothyroidism. 7/34 (20.3%) had central secondary adrenal insufficiency and 2/34 (5.8%) had primary adrenal insufficiency. Central hypogonadism was found in 18/31 (58.1%) of patients, whereas 6/31 (19.4%) had primary hypogonadism. Growth hormone deficiency was found in 7/59 (29.7%) patients and 4/27 (14.8%) patients had hyperprolactinemia. Imaging revealed involvement of the pituitary/hypothalamus in 18 (21.7%) patients, adrenal glands in 18 (21.7%) patients and testicles in 5 (6.0%) patients. Thirty-five patients (42.2%) had at least one gland involved seen on imaging, Visible gland infiltration did not correlate with hormonal deficiencies. New hormonal deficits appeared during follow-up. Conclusions: This is the largest case series of endocrine manifestations in patients with ECD. Endocrine involvement is frequent in these patients, 57.8% have at least one hormonal deficiency. Because endocrine abnormalities can evolve throughout the course of the disease, patients should have endocrine evaluation periodically.

SAT-LB100 Suspicious Thyroid Nodules: Management Since the Introduction of 2015 ATA Guidelines

Objective: In 2015, updated American Thyroid Association (ATA) guidelines recommended observation for suspicious sub-centimeter thyroid nodules based on their indolent course. Evaluation of individual patient factors and nodule invasiveness should guide clinician decision-making about biopsy. We aimed to evaluate frequency of biopsy in suspicious thyroid nodules since the introduction of these guidelines, including factors contributing to clinical decision making in a tertiary care center. Methods: Retrospective study of patients in a tertiary medical center with new, suspicious thyroid nodules between March 1, 2015, and July 1, 2017. We identified suspicious nodules ≤ 1 cm, not previously biopsied. Suspicious nodules were defined as those 1) mentioned suspicious by radiology, 2) hypoechoic nodules with ≥ 1 worrisome feature mentioned by radiology, or 3) with worrisome neck lymph nodes. Results/Discussion: We identified a total of 138 nodules in 127 patients: mean age 58.2 ± 14.2, 73% female, 87% Caucasian, and mean Charlton Comorbidity Index 2.4 ± 2.3, corresponding with 77-90% 10 year survival. Thyroid nodule characteristics included 88% hypoechoic, 47% micro-calcifications, 28% irregular margins, and 26% peripheral calcifications; 57% were located ≤1 mm from thyroid edge. Frequency of biopsy in suspicious thyroid nodules was 38%. Ultrasound features associated with increased likelihood of biopsy included larger nodule volume (0.18 vs 0.13cm³, p=0.01) and presence of concerning lymph nodes (69% vs 31%, p<0.01). Patient’s age and degree of comorbidities did not change likelihood for biopsy. Frequency of biopsy did not vary by type of provider (endocrinologist vs other) or trigger for thyroid nodule diagnosis (incidental vs. non incidental). Among 85 nodules that were not biopsied, 41% did not have specific recommendation for follow-up, and the remainder were recommended for follow-up ultrasounds in 3-6 months (19%), 7-12 months (19%), and >12 months 21%. Only one quarter of those who were recommended repeat ultrasound had documented re-evaluation. Conclusion: One third of suspicious thyroid nodules underwent biopsy since release of updated ATA guidelines. Factors driving thyroid biopsy seems to be associated with nodule characteristics but not with patient’s factors including age and comorbidities. Patients who did not have biopsy had inconsistent follow up regimens, and many did not have any follow up plan. Further studies and development of decision aides may be helpful in providing an individualized approach for suspicious thyroid nodules. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Extensive clinical experience: Hypothalamic-pituitary-adrenal axis recovery after adrenalectomy for corticotropin-independent cortisol excess

OBJECTIVE

To identify predictors of hypothalamic-pituitary-adrenal (HPA) axis recovery interval and severity of glucocorticoid withdrawal symptoms (GWS) in patients undergoing adrenalectomy for corticotropin-independent cortisol excess.

DESIGN

This is a retrospective study of patients with mild autonomous cortisol excess (MACE), moderate and severe Cushing syndrome (CS) who developed adrenal insufficiency after unilateral adrenalectomy between 1998 and 2017.

RESULTS

Adrenalectomy was performed in 81 patients (79% women, median age 52 years [IQR 42-62]). HPA axis recovery occurred at a median of 4.3 months (IQR 1.6-11.4) after adrenalectomy (severe CS vs moderate CS vs MACE: median 11.4 vs 2.8 vs 2.1 months, P < 0.01). Main predictors of HPA axis recovery interval included: preoperative serum cortisol concentration after 1-mg overnight dexamethasone suppression test >10 μg/dL or >276 nmol/L (9.7 vs 1.3 months if cortisol ≤10 μg/dL or ≤276 nmol/L, P < 0.01); body mass index (for every 3 kg/m² decrease, glucocorticoid taper increased by 1 month, P < 0.05); age <45 (11.4 vs 2.3 months if ≥45 years, P < 0.05); duration of symptoms prior to diagnosis >1 year (11.4 vs 2.8 months if ≤1 year); moon facies (11.4 vs 2.2 months if no rounding of the face); and myopathy (13.1 vs 2.7 months if no myopathy, P < 0.05). Patients with severe CS had a higher incidence of GWS compared to patients with MACE (66.7% vs 40.0%, P < 0.05) with a median of 1 and 0 events/patient, respectively.

CONCLUSIONS

The HPA axis recovery interval was the longest for patients with severe CS. Surprisingly, patients with moderate CS recovered their HPA axis as quickly as those with MACE. Glucocorticoid withdrawal symptoms were observed in all groups, with more events in patients with severe CS. This study emphasizes the need to counsel patients on expectations for HPA axis recovery and address intervention for GWS based on individual preoperative parameters.

Molecular characterization of the PK-LR gene in pyruvate kinase deficient Spanish patients. Red Cell Pathology Group of the Spanish Society of Haematology (AEHH)

The PK-LR gene has been studied in 12 unrelated patients with red cell pyruvate kinase deficiency and hereditary nonspherocytic haemolytic anaemia (CNSHA). The entire codifying region of the R-type PK gene and the flanking intronic regions were analysed by single-stranded conformation polymorphism (SSCP) followed by direct sequencing of abnormal DNA. 10 different mutations were identified in 22/24 alleles at risk. Eight of these were missense mutations that caused the following single amino acid changes: G514C (172Glu-Gln), G1010A (337Arg-Gln), G1015C (339Asp-Gln), T1070C (357Ile-Thr), C1223T (408Thr-Ile), G1291A (431Ala-Thr), C1456T (486Arg-Trp) and G1595A (532Arg-Gln). Two were nonsense mutations: G721T (241Glu-Stop) and C1675T (559Arg-Stop). 7/22 alleles demonstrated the same C1456 --> T mutation. The study of the polymorphic site at nucleotide (nt) 1705 performed in all cases disclosed a 1705 C/C mutation in 10 and a 1705 A/C mutation in three. This is the first report on the presence of several different L-type PK gene mutations within Spanish population. Furthermore, from the PK gene mutations found, six were unique and not previously described (1015C, 1070C, 1223T, 1291A, 1595A and 1675T) and one (C1456T) seems to be predominant in Spain. Interestingly, no case with the 1529A mutation commonly found in Northern European populations was present here.