Vitamin D levels and the risk of prostate cancer and prostate cancer mortality

BACKGROUND

Vitamin D has a role in bone turnover and potentially bone-metastatic spread of prostate cancer (PCa). The aim of this observational study was to address the association between levels of serum vitamin D, diagnosis of PCa and subsequent mortality in men who underwent a biopsy of the prostate.

METHODS

All men who underwent prostatic biopsy in the Danish PCa Registry (DaPCaR) and who had a serum vitamin D measurement during the period 2004 to 2010 (n = 4,065) were identified. Men were categorized by clinical cut-offs based on seasonally adjusted serum vitamin D levels in <25 (deficient), 25-50 (insufficient), 50-75 (sufficient) and >75 nmol/L (high) serum vitamin D. Logistic regression model for association between vitamin D and risk of PCa diagnosis and multivariate survival analyses were applied.

RESULTS

No association between serum vitamin D and risk of PCa was found. Overall survival was lowest for serum vitamin D deficiency and a significantly higher PCa specific mortality (HR: 2.37, 95%CI: 1.45-3.90, p < .001) and other cause mortality (HR: 2.08, 95%CI: 1.33-3.24, p = .001) was found for PCa patients with serum vitamin D deficiency compared to serum vitamin D sufficiency.

CONCLUSION

No association was found between serum vitamin D categories and risk of PCa in men who underwent biopsy of the prostate. Men with PCa and serum vitamin D deficiency had a higher overall and PCa specific mortality compared to men with a sufficient level of serum vitamin D.

Contribution of remnant cholesterol to cardiovascular risk

BACKGROUND

Remnant cholesterol in triglyceride-rich lipoproteins is associated observationally and genetic, causally with increased risk of atherosclerotic cardiovascular disease in healthy individuals.

OBJECTIVES

We tested the hypothesis that an unmet medical need exists in individuals with high nonfasting remnant cholesterol and prior atherosclerotic cardiovascular disease.

METHODS

From amongst 109 574 individuals in a prospective cohort study of the Danish general population, we included 2973 individuals aged 20-80 with baseline diagnoses of myocardial infarction/ischaemic stroke ascertained from national Danish health registries.

RESULTS

The recurrent major cardiovascular event (MACE) incidence rates per 1000 person-years were 39 (95% confidence interval: 30-50) for individuals with remnant cholesterol levels ≥ 1.5 mmol L^-1 (≥58 mg dL^-1 ), 31 (26-37) for 1-1.49 mmol L^-1 (39-57 mg dL^-1 ), 27 (24-31) for 0.5-0.99 mmol L^-1 (19-38 mg dL^-1 ) and 23 (19-27) for individuals with remnant cholesterol < 0.5 mmol L^-1 (<19 mg dL^-1 ). Compared to individuals with remnant cholesterol < 0.5 mmol L^-1 (<19 mg dL^-1 ), the subhazard ratio for recurrent MACE was 1.23 (95% CI: 0.98-1.55) for individuals with remnant cholesterol levels of 0.5-0.99 mmol L^-1 (19-38 mg dL^-1 ), 1.48 (1.14-1.92) for 1-1.49 mmol L^-1 (39-57 mg dL^-1 ) and 1.79 (1.28-2.49) for ≥ 1.5 mmol L^-1 (≥58 mg dL^-1 ). The recurrent MACE incidence rates per 1000 person-years for individuals with remnant cholesterol levels < 0.5 mmol L^-1 (<19 mg dL^-1 ) and ≥ 1.5 mmol L^-1 (≥58 mg dL^-1 ) were 10 (6.6-15) and 31 (21-47) for those below age 65 and correspondingly 25 (21-30) and 43 (32-59) for those with LDL cholesterol levels < 3 mmol L^-1 (<116 mg dL^-1 ), respectively. For a 20% recurrent MACE risk reduction in secondary prevention, an estimated remnant cholesterol lowering of 0.83 mmol L^-1 (32 mg dL^-1 ) would be needed.

CONCLUSIONS

In individuals with a diagnosis of myocardial infarction/ischaemic stroke, a lower remnant cholesterol of 0.8 mmol L^-1 (32 mg dL^-1 ) was estimated to reduce recurrent MACE by 20% in secondary prevention. Our data indicate an unmet medical need for secondary prevention in individuals with high nonfasting remnant cholesterol levels.

5131Unmet need for secondary prevention in individuals from the general population with increased lipoprotein(a): a contemporary population-based study

Background

There is strong evidence linking high lipoprotein(a) (Lp(a)) to development of incident cardiovascular disease (CVD), but it is not clear whether Lp(a) is associated with risk of recurrent CVD events in individuals from the general population with preexisting CVD. This is of importance as the first drugs specifically aimed at lowering Lp(a) are currently in development, and these would likely be used primarily in individuals with established CVD for secondary prevention of recurrent CVD events.

Purpose

We tested the hypothesis that high concentrations of Lp(a) are associated with high risk of recurrent CVD in individuals from the general population with preexisting CVD.

Methods

From the Copenhagen General Population Study (CGPS) (2003–2015) of 58,527 individuals with measurements of Lp(a) at baseline, 2,527 aged 20–79 with a history of CVD were studied. The primary endpoint was major adverse cardiovascular event (MACE). We also studied 1,115 individuals with CVD at baseline from the Copenhagen City Heart Study (CCHS) (1991–1994) and the Copenhagen Ischemic Heart Disease Study (CIHDS) (1991–1993).

Results

During a median follow-up of 5 years (range: 0–13, 13,974 person-years), 493 individuals (20%) experienced a MACE in the CGPS. MACE incidence rates per 1,000 person-years were 29 (95% CI: 25–34) for individuals with Lp(a) <10mg/dL (<18nmol/L), 35 (30–41) for 10–49mg/dL (18–104nmol/L), 42 (34–51) for 50–99mg/dL (105–213nmol/L), and 54 (42–70) for ≥100mg/dL (≥214nmol/L) (see Figure). Compared to individuals with Lp(a) <10mg/dL (<18nmol/L), the MACE incidence rate ratios were 1.21 (0.98–1.50) for 10–49mg/dL (18–104nmol/L), 1.43 (1.12–1.82) for 50–99mg/dL (105–213nmol/L), and 1.85 (1.38–2.49) for ≥100mg/dL (≥214nmol/L). Independent confirmation was obtained in individuals from the CCHS and CIHDS with MACE incidence rates per 1,000 person-years of 94 (95 CI: 84–106) for individuals with Lp(a) <10mg/dL (<18nmol/L), 115 (103–129) for 10–49mg/dL (18–104nmol/L), 134 (115–156) for 50–99mg/dL (105–213nmol/L), and 140 (116–169) for ≥100mg/dL (≥214nmol/L).

Conclusion

High concentrations of Lp(a) are associated with high risk of recurrent CVD in individuals from the general population with preexisting CVD. This points to a possible unmet need for secondary prevention in individuals with increased Lp(a), and such individuals could be a target group for upcoming randomized cardiovascular outcome trials.

Acknowledgement/Funding

The Novo Nordisk Foundation, Herlev and Gentofte Hospital, Chief Physician Johan Boserup and Lise Boserup's Fund

History of cardiovascular disease and cardiovascular biomarkers are associated with 30-day mortality in patients with hip fracture

Hip fractures are associated with increased mortality and it is important to identify risk factors. This study demonstrates that preexisting cardiovascular disease as well as cardiovascular biomarkers that are associated with increased 30-day mortality. These findings can be used to identify high-risk patients who might benefit from specialized care.

INTRODUCTION

This study investigates the association between cardiovascular disease (CVD), cardiovascular biomarkers, and 30-day mortality following a hip fracture.

METHODS

The Danish National Patient Registry was used to investigate the association between CVD and mortality following hip fracture in a nationwide population-based cohort study. In a subset of the included patients (n = 355), blood samples were available from a local biobank. These samples were used for analyzing the association between specific biochemical markers and mortality. The primary outcome was 30-day mortality.

RESULTS

A total of 113,211 patients were included in the population-based cohort study. Among these, heart failure was present in 9.4%, ischemic heart disease in 15.9%, and ischemic stroke in 12.0%. Within 30 days after the hip fracture, 11,488 patients died, resulting in an overall 30-day mortality of 10.1%. The 30-day mortality was significantly increased in individuals with preexisting CVD with multivariably adjusted odds ratios of 1.69 (95% confidence interval, 1.60-1.78) for heart failure, 1.23 (1.17-1.29) for ischemic heart disease, and 1.06 (1.00-1.12) for ischemic stroke. In the local database including 355 patients, 41 (11.5%) died within 30 days. The multivariably adjusted odds ratio for 30-day mortality increased with increasing NT-proBNP (2.36 [1.53-3.64] per quartile) and decreased with increasing HDL cholesterol (0.58 [0.41-0.82] per quartile). On this basis, we established a model for predicting the probability of death based on the biochemical markers.

CONCLUSION

Preexisting CVD was associated with increased 30-day mortality after a hip fracture. Furthermore, high levels of NT-proBNP and low levels of HDL cholesterol were associated with increased 30-day mortality.

Vitamin D levels and cancer incidence in 217,244 individuals from primary health care in Denmark

Vitamin D has been linked to cancer development in both pre-clinical and epidemiological studies. Our study examines the association between serum levels of vitamin D and cancer incidence in the Capital Region of Denmark. Individuals who had vitamin D analyzed at The Copenhagen General Practitioners Laboratory between April 2004 and January 2010 were linked to Danish registries with end of follow-up date at Dec 31st 2014, excluding individuals with pre-existing cancer. Cox regression models adjusted for age in one-year intervals, sex, month of sampling, and Charlson Comorbidity Index were applied. The study population of 217,244 individuals had a median vitamin D level of 46 nmol/L (IQR 27-67 nmol/L). Non-melanoma skin cancer was the most frequent form of cancer, followed by breast-, lung-, and prostate cancers. No associations were found between increments of 10 nmol/L vitamin D and incidence of breast, colorectal, urinary, ovary or corpus uteri cancer. However, higher levels of vitamin D were associated with higher incidence of non-melanoma (HR 1.09 [1.09-1.1]) and melanoma skin cancer (HR 1.1 [1.08-1.13]) as well as prostate (HR 1.05 [1.03-1.07]) and hematological cancers (HR 1.03 [1.01-1.06]), but with lower incidence of lung cancer (HR 0.95 [0.93-0.97]). In our study, vitamin D levels are not associated with the incidence of several major cancer types, but higher levels are significantly associated with a higher incidence of skin, prostate, and hematological cancers as well as a lower incidence of lung cancer. These results do not support an overall protective effect against cancer by vitamin D.

Hyperkalemia is Associated with Increased 30-Day Mortality in Hip Fracture Patients

Abnormal plasma concentrations of potassium in the form of hyper- and hypokalemia are frequent among hospitalized patients and have been linked to poor outcomes. In this study, we examined the prevalence of hypo- and hyperkalemia in patients admitted with a fractured hip as well as the association with 30-day mortality in these patients. A total of 7293 hip fracture patients (aged 60 years or above) with admission plasma potassium measurements were included. Data on comorbidity, medication, and death was retrieved from national registries. The association between plasma potassium and mortality was examined using Cox proportional hazards models adjusted for age, sex, and comorbidities. The prevalence of hypo- and hyperkalemia on admission was 19.8% and 6.6%, respectively. The 30-day mortality rates were increased for patients with hyperkalemia (21.0%, p < 0.0001) compared to normokalemic patients (9.5%), whereas hypokalemia was not significantly associated with mortality. After adjustment for age, sex, and individual comorbidities, hyperkalemia was still associated with increased risk of death 30 days after admission (HR = 1.93 [1.55-2.40], p < 0.0001). After the same adjustments, hypokalemia remained non-associated with increased risk of 30-day mortality (HR = 1.06 [0.87-1.29], p = 0.6). Hyperkalemia, but not hypokalemia, at admission is associated with increased 30-day mortality after a hip fracture.

Biased agonism and allosteric modulation of G protein-coupled receptor 183 - a 7TM receptor also known as Epstein-Barr virus-induced gene 2

BACKGROUND AND PURPOSE

The GPCR Epstein-Barr virus-induced gene 2 (EBI2, also known as GPR183) is activated by oxysterols and plays a pivotal role in the regulation of B cell migration during immune responses. While the molecular basis of agonist binding has been addressed in several studies, the concept of biased agonism of the EBI2 receptor has not been explored.

EXPERIMENTAL APPROACH

We investigated the effects of the EBI2 endogenous agonist 7α,25-dihydroxycholesterol (7α,25-OHC) on G protein-dependent and -independent pathways as well as sodium ion allosterism using site-directed mutagenesis and functional studies. Moreover, we generated a homology model of the EBI2 receptor to investigate the structural basis of the allosteric modulation by sodium.

KEY RESULTS

Residue N114, located in the middle of transmembrane-III at position III:11/3.35, was found to function as an efficacy switch. Thus, substituting N114 with an alanine (N114A) completely abolished heterotrimeric G protein subunit Gi α activation by 7α,25-OHC even though the specific binding of [³ H]-7α,25-OHC increased. In contrast, the N114A mutant was still able to recruit β-arrestin and even had an enhanced potency (18.7-fold) compared with EBI2 wild type. Sodium had a negative allosteric effect on oxysterol binding that was mediated via N114, verifying the key role of N114. This was further supported by molecular modelling of the ion binding site based on a EBI2 receptor homology model.

CONCLUSIONS AND IMPLICATIONS

Collectively, our data point to N114 as a key residue for EBI2 signalling controlling the balance between G protein-dependent and -independent pathways and facilitating sodium binding.

Temporal trends in the use of antithrombotics at admission

Background and purpose - Currently, no clear evidence exists on the pattern of use of antithrombotics at admission in hip fracture patients and how this has changed over time. We investigated temporal trends in-and factors associated with-the use of antithrombotics in patients admitted with a fractured hip. Patients and methods - This was a population-based cohort study including all patients aged 18 years or above who were admitted with a hip fracture in Denmark from 1996 to 2012. The Danish national registries were used to collect information on medication use, vital status, and comorbidity. Results - From 1996 to 2012, the proportion of patients using antithrombotics in general increased by a factor of 2.3 from 19% to 43% (p < 0.001). More specifically, the use of anticoagulants increased by a factor of 6.8 and the use of antiplatelets increased by a factor of 2.1. When we adjusted for possible confounders, the use of antithrombotics still increased for every calendar year (relative risk (RR) = 1.03, CI: 1.03-1.04; p < 0.001). Age, sex, and Charlson comorbidity index were all associated with the use of antithrombotics (all p < 0.001). Interpretation - The proportion of hip fracture patients using antithrombotics at admission has increased substantially in Denmark over the last 2 decades. This highlights the need for evidence-based guidelines on how to handle patients using antithrombotics to ensure safe surgery and to avoid surgical delay.

Orthogeriatric Service Reduces Mortality in Patients With Hip Fracture

Introduction:

Orthogeriatric service has been shown to improve outcomes in patients with hip fracture. The purpose of this study is to evaluate the effect of orthogeriatrics at Bispebjerg University Hospital, Denmark. The primary outcome is mortality inhospital and after 1, 3, and 12 months for patients with hip fracture. The secondary outcome is mortality for home dwellers and nursing home inhabitants.

Materials and Methods:

This is a retrospective clinical cohort study with an historic control group including all patients with hip fracture admitted from 2007 to 2011. Patients with hip fracture are registered in a local database, and data are retrieved retrospectively using the Danish Civil Registration Number.

Results:

We included 993 patients in the intervention group and 989 patients in the control group. A univariate analysis showed only significantly decreased mortality inhospital 6.3% vs 3.1% (P = .009) after orthogeriatrics. However, when adjusting for age, gender, and American Society of Anaesthesiologists (ASA) score in a multivariate analysis, including all patients with hip fracture, we find significantly reduced mortality inhospital (odds ratio [OR] 0.35), after 30 [OR 0.66] and 90 days [OR 0.72] and 1 year [OR 0.79]). When using a univariate analysis for home-dwelling patients, we found significantly reduced mortality inhospital (8.3-2.0%, P < .0001), after 30 days (12.2-6.8%, P = .004) and 90 days (20.5-13.0%, P = .002). One-year mortality was not significant. Patients from nursing homes had no significant decreasing mortality at any point of time in the univariate analysis.

Conclusion:

We have shown significant decreases for inhospital, 30 day, 90 day, and 1-year mortality after implementation of orthogeriatric service at Bispebjerg Hospital when adjusting for age, gender, and ASA score. Future trials should include frail patients with other fracture types who can benefit from orthogeriatrics.

Hyponatremia and hypernatremia are associated with increased 30-day mortality in hip fracture patients

Using data from the Danish national registries on 7317 patients, this study shows that abnormal plasma sodium levels, in the form of hyponatremia and hypernatremia, are prevalent and associated with increased 30-day mortality in hip fracture patients.

INTRODUCTION

The aim of this study was to examine the prevalence of hyponatremia and hypernatremia in patients admitted with a fractured hip as well as the association with 30-day in mortality in these patients.

METHODS

A total of 7317 hip fracture patients (aged 60 years or above) with admission plasma sodium measurements were included. Data on comorbidity, medication, and death was retrieved from Danish national registries. The association between plasma sodium and mortality was examined using Cox proportional hazard models.

RESULTS

The prevalence of hyponatremia and hypernatremia on admission was 19.0 and 1.7 %, respectively. Thirty-day mortality was increased for patients with hyponatremia (12.2 %, p = 0.005) and hypernatremia (15.5 %, p = 0.03) compared to normonatremic patients (9.6 %). After adjustment for possible confounding factors, hyponatremia (1.38 [1.16-1.64], p = 0.0003) and hypernatremia (1.71 [1.08-2.70], p = 0.02) were still associated with increased risk of death by 30 days. Looking at the association between changes in plasma sodium during admission and mortality, there was no difference between patients with normalized and persistent hyponatremia (10.4 vs 11.3 %, p = 0.6) while a lower mortality was found for normalized hypernatremia compared to persistent hypernatremia (12.4 vs 33.3 %, p = 0.03).

CONCLUSIONS

This study shows that abnormal plasma sodium levels are prevalent in patients admitted with a fractured hip and that both hyponatremia and hypernatremia are associated with increased risk of death within 30 days of admission.

Secondary hyperparathyroidism and mortality in hip fracture patients compared to a control group from general practice

INTRODUCTION

Previously, little attention has been paid as to how disturbances in the parathyroid hormone (PTH)-calcium-vitamin D-axis, such as secondary hyperparathyroidism (SHPT), relate to mortality amongst hip fracture patients. This study aimed to (1) determine if SHPT is associated with mortality in this group of patients, (2) investigate the association between serum (s-) PTH, s-total calcium, s-25-hydroxyvitamin D (s-25(OH)D) and mortality and (3) determine the prevalence of SHPT amongst hip fracture patients and a control group.

METHOD

The study included 562 hip fracture patients (HF) (age ≥ 70 years) admitted to a Danish university hospital. The hip fracture patients were prospectively enrolled in a dedicated hip fracture database. Each hip fracture patient was exactly matched according to age and sex with two controls randomly chosen from a control population of 21,778 subjects who had s-PTH, s-total calcium and s-25(OH)D measured at the Copenhagen General Practitioners Laboratory after referral from their general practitioner. The control group (Con) thus consisted of 1124 subjects.

RESULTS

General 1-year mortality: Con-female 8.4%, Con-male 15.3%, HF-female 24.6%, HF-male 33.3%, p<0.0001 (log rank). SHPT AND RELATED 1-YEAR MORTALITY: Con-no SHPT 8.9%, Con-SHPT 16.8%, HF-no SHPT 22.7%, HF-SHPT 34.9%, p<0.0001 (log rank). The mortality rates were higher for controls with SHPT (OR 2.06, 95% CI: 1.32-3.23), hip fracture patients without SHPT (OR 3.00, 95% CI: 2.14-4.20) and hip fracture patients with SHPT (OR 5.46, 95% CI: 3.32-8.97) compared to the controls without SHPT. PREVALENCE OF SHPT: Con 16%, HF 20%, p=0.09 (Chi-square).

CONCLUSIONS

Our study clearly shows that SHPT is significantly associated with mortality in both hip fracture patients and the control group. In the multivariate Cox regression analysis, s-PTH and s-total calcium were both significantly associated with mortality, whereas s-25(OH)D was not associated with mortality in this analysis. Our study furthermore indicates that SHPT is almost equally prevalent amongst the hip fracture patients and the control group.

An epidemiological study of congenital anorectal malformations: 15 Danish birth cohorts followed for 7 years

In the county of Fyn (about 500,000 inhabitants) which is a well defined and representative 10% sample of the total Danish population, 15 total birth cohorts were scrutinized for the occurrence of anorectal malformations (ARM). All the patients were followed until the age of 7 or death. In a total of 96,073 births, 29 cases were observed; one concordant monozygotic pair was counted as one case. The study showed the point prevalence at birth to be 3.0 per 10,000; almost the same frequency has been found in Sweden whereas other figures from Europe and North America are lower. Children with ARM have in general a poor prognosis, largely due to the many associated anomalies. In this material, 11 of 12 isolated ARM cases survived until age 7, but five of these had significant handicaps. Out of 17 probands with associated anomalies, only seven survived until age 7, all of them having some handicap. This group of patients spent at least 15 times more days in hospital than an age-matched group from the same region until age 7, and they underwent a considerable number of operations. The study showed an increased frequency of chromosome anomalies among children with ARM.

Secondary surgery in advanced testicular germ-cell tumors

Twenty-four patients with residual tumor after intensive chemotherapy for advanced testicular germ-cell tumors were subjected to secondary surgery. Twenty patients had complete resection with the following distribution of histological types: 4 embryonal carcinoma, 9 mature teratoma and 7 fibrous tissue. Eighteen of these patients remain free of disease. Four patients had incomplete resection. Two of these patients with embryonal carcinoma died later despite further treatment; 2 patients with teratoma remain free of disease. Secondary surgery is recommended in cases where residual tumor is found after intensive chemotherapy and where tumor markers are not elevated.

Serum thyroglobulin in patients undergoing subtotal thyroidectomy for toxic and nontoxic goiter

Twenty-five patients with nontoxic nodular goiters and six with toxic goiter were studied prior to subtotal thyroidectomy, with closely spaced blood sampling up to three weeks after surgery, and approximately one year after surgery. Serum thyroglobulin (Tg) was measured by a previously described radioimmunological method. The mean serum Tg was elevated in patients with nontoxic nodular and toxic goiters compared to sex and age matched control groups with pronounced increases during surgery. The disappearance curves of Tg in both groups had two exponentials, an initial steep slope with a half-life of 4.0 +/- 1.8 (SD) h in nontoxic goiter and 4.5 +/- 3.2 h in toxic goiter. This was followed by a more shallow slope with a half-life of 3.6 +/- 1.1 days in nontoxic goiter and 3.4 +/- 0.8 h in toxic goiter, the breaking point between the slopes lying approximately at 48-72 h. There was no significant difference between the half-life of Tg in patients with toxic or nontoxic goiters, respectively. There was a weak correlation between the weight of the removed thyroid tissue and the maximally obtained Tg concentration at the time of surgery, but no correlation with the levels before operation. Serum Tg was significantly lower three weeks after operation and approximately one year after surgery. In conclusion, different forms of the Tg molecules seem to be removed at different rates, independent on the type of goiter.

Sequential changes in serum thyroglobulin (Tg) and its autoantibodies (TgAb) following subtotal thyroidectomy of patients with preoperatively detectable TgAb

The changes in serum concentrations of thyroglobulin antibodies (TgAb) were investigated in eight patients with various thyroid disorders before, during and after thyroid surgery. TgAb was measured by a radioassay using 125I-thyroglobulin. In six patients the TgAb decreased rapidly during operation. Of these patients four had low concentrations pre-operatively, and the decrease in TgAb resulted in undetectable concentrations for more than 2 days, Serum thyroglobulin (Tg), measured in the specimens with undetectable TgAb, i.e immediately following surgery, showed concentration vs time curves resembling curves from patients with no antibody present. Furthermore, two of these patients had such a high concentration of TgAb pre-operatively that the initial Tg release was not sufficient to remove the TgAb, resulting in detectable TgAb throughout the investigation period. Serum samples drawn during and after operation were chromatographed according to molecular size, showing measureable Tg corresponding to 19S Tg. TgAb was only measureable in fractions corresponding to 7S IgG. The expected presence of complexed Tg and TgAb could not be demonstrated, but the analytical methods might have been unable to reveal this. The remaining two patients with thyroiditis showed no decrease in TgAb. This was compatible with a low content of Tg in the throid measured in one of them.

Thyroglobulin of varying molecular sizes with different disappearance rates in plasma following subtotal thyroidectomy

To investigate the possible presence of thyroglobulin (Tg of different molecular sizes in plasma, blood specimens were drawn from patients during and after surgery for thyroid adenoma. Tg was measured in all serum samples by a radioimmunoassay. Selected samples were fractionated on a sepharose CL-6B column, and the fractions were assayed for Tg antigen. In serum drawn at maximum Tg concentration, molecular weights of Tg antigen ranging from 660,000 (19S) to less than 100,000 were found. 6 h later the Tg antigen of mol. wt. less than 100,000 could not be detected, and after 3 days only 19S Tg was present. Correspondingly the plasma Tg concentration vs. time curve showed a biphasic course from which two half-lives could be estimated. For 19S Tg, ta1/2 had a mean value of 4.3 days, whereas the over-all half-life for the mixture of smaller molecules, tb1/2, had a mean value of 3.7 h. The smaller molecules also showed different antigenic reactivity in the assay indicating an altered structure of the molecules. The assumption that this might be due to lack of sialic acid would explain the faster catabolic rate.