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Biomedical subjects

S L Blethen

Publications and source records attributed to S L Blethen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Regulation of the acid-labile subunit of the insulin-like growth factor ternary complex in patients with insulin-dependent diabetes mellitus and severe burns.

OBJECTIVE: Little information is available regarding the regulation of serum acid-labile subunit (ALS) in human disease. We have studied alterations in serum ALS of the insulin-like growth factor (IGF) ternary complex in children with untreated insulin-dependent diabetes mellitus (IDDM) and subjects with severe burns before and after insulin therapy. In addition, we have investigated the effect of insulin plus GH on serum ALS in burn patients. DESIGN: Serum samples were obtained from children with newly diagnosed and untreated IDDM before the initiation of insulin therapy and 1 month thereafter. Serum samples were also obtained from adult patients with severe burns who were on a continuous infusion of a carbohydrate-rich enteral diet via nasogastric and duodenal catheters under basal conditions, after a 1-week period of continuous insulin infusion, and after an additional week of insulin plus recombinant GH. PATIENTS: Twenty children and adolescents with untreated IDDM, aged 1.2-16 years, and 6 young adult patients with severe burns aged 17-28 years were studied longitudinally. Control sera were obtained from age, sex and pubertal status matched subjects (for children with IDDM) and from fed healthy adults. MEASUREMENTS: Serum insulin, GH, cortisol and IGF-I were measured by radioimmunoassay, and serum ALS levels were assessed by Western immunoblot before and after treatment periods. RESULTS: Serum ALS levels were lower in untreated children with IDDM (69 +/- 6% of control children). Insulin therapy significantly increased serum ALS (79 +/- 5%, P < 0.05) in these children. Patients with severe burns also had lower serum ALS levels (79 +/- 10% of control adults). After one week of insulin therapy serum ALS levels increased to 90 +/- 15% of control values (P < 0.05). Addition of GH to insulin therapy for another week did not significantly further increase serum ALS levels (95 +/- 27%). Serum IGF-I concentrations increased nearly 2.5-fold in diabetic subjects and fourfold in burn subjects at the end of the study periods. There were no proteolytic fragments of ALS in the sera studied. The deglycosylation pattern of ALS did not differ between diabetic and control sera. CONCLUSION: Serum ALS levels were diminished in children with untreated IDDM and were partially restored after the initiation of insulin therapy. Serum ALS levels were also diminished in patients with severe burn injury and restored by insulin treatment. Addition of GH to insulin therapy did not significantly increase serum ALS levels over levels obtained during insulin therapy alone. These decreases in serum ALS were smaller than the decrease in serum IGF-I concentrations in both conditions, suggesting that IGF-I is the limiting factor for the ternary complex formation in the catabolic states. Insulin may regulate circulating ALS levels in catabolic states and helps to restore the IGF system.

Acute Disease↗
PubMed1996

Insulin treatment normalizes reduced free insulin-like growth factor-I concentrations in diabetic children.

OBJECTIVE: We have recently demonstrated multiple aberrations in the GH-IGF axis in the sera of children with untreated insulin-dependent diabetes mellitus (IDDM) which were restored after insulin replacement. However, the net result of these alterations in the IGF system on the concentrations of free/biologically available IGF-I in the serum have not been examined directly in diabetic children. In the present study, the effect of diabetes and subsequent insulin replacement on the circulating free IGF-I concentrations are assessed. DESIGN: Fasting venous serum samples were obtained longitudinally, before and at various times after the initiation of insulin treatment in untreated diabetic subjects. SUBJECTS: Ten prepubertal, aged (mean +/- SEM) 6.3 +/- 1.0 years, and six adolescent, aged 12.7 +/- 1.1 years, subjects with newly diagnosed and untreated IDDM, and age and pubertal status-matched control children and adolescents were recruited. METHODS: The serum samples were collected before initiating insulin treatment and 12-24 h, 1 week, and 1 month thereafter in subjects with IDDM. Insulin doses ranged from 0.5 to 1.2 U/kg/day. MEASUREMENTS: Free IGF-I concentration was assayed by a recently developed two-site immunoradiometric assay. Total IGF-I was measured by radioimmunoassay after acid-ethanol extraction of binding proteins. Differences in free and total IGF-I concentrations in IDDM subjects before and during insulin treatment were analysed by repeated measures analysis of variance followed by pairwise multiple comparisons test. In seven subjects with IDDM, where serum IGFBP-1 and IGFBP-3 concentrations, and IGFBP-3 protease activity had also been measured in a previous study, the relationship between these variables and circulating free IGF-I concentrations were examined by linear regression analysis. RESULTS: Free IGF-I concentrations in prepubertal subjects with IDDM were 0.9 +/- 0.2, 1.5 +/- 0.3, 1.6 +/- 0.3 and 2.5 +/- 0.4 micrograms/l before, 1 day, 1 week and 1 month after insulin treatment, respectively. Free IGF-I concentrations of control prepubertal children were 2.6 +/- 0.5 micrograms/l. Pubertal subjects had higher free IGF-I concentrations than prepubertal subjects but demonstrated a similar type of pattern; before insulin 2.3 +/- 1.1, 1 day 3.8 +/- 1.3, 1 week 3.7 +/- 0.6, 1 month 6.5 +/- 1.5 vs pubertal controls 7.7 +/- 2.0 micrograms/l. Total IGF-I concentrations were also reduced in untreated diabetic subjects and showed a slower pattern of normalization than free IGF-I concentrations. Free IGF-I concentrations correlated positively with total IGF-I and negatively with IGFBP-1 concentrations. There was no significant correlation between free IGF-I and either serum IGFBP-3 concentrations or IGFBP-3 protease activity. CONCLUSION: Alterations in the IGF system during untreated IDDM lead to a reduction in circulating free IGF-I concentrations which is restored progressively during insulin treatment. An increase in free IGF-I precedes that of total IGF-I suggesting that the former is a more sensitive indicator of the metabolic status. An inverse correlation between free IGF-I and IGFBP-1 supports the hypothesis that IGFBP-1 plays an important role in the acute modulation of free IGF-I levels.

Adolescent↗
PubMed1996

Slipped capital femoral epiphysis in children treated with growth hormone. A summary of the National Cooperative Growth Study experience.

We examined the association between slipped capital femoral epiphysis (SCFE) and growth hormone (GH) treatment in 16,514 children who had not been treated with GH prior to their enrollment in the National Cooperative Growth Study. Fifteen children had SCFE prior to receiving GH therapy, 26 developed SCFE during GH treatment, and one had SCFE on one side prior to GH treatment and developed it on the contralateral side while receiving GH. Children with GH deficiency were significantly more likely to develop SCFE while on GH treatment than were children with idiopathic short stature (p = 0.006). There was no difference between GH-deficient girls and boys in the risk of developing SCFE during GH treatment. There were 3 cases of SCFE in girls with Turner syndrome before GH treatment and 3 during. Typically, children who developed SCFE while on GH were older, heavier, and grew more slowly during the first year of GH than those who did not. Children with GH deficiency, Turner syndrome, and other known causes of short stature are more likely to develop SCFE before or during GH treatment than children with idiopathic short stature.

Adolescent↗
PubMed1996

Molecular genetics and pathophysiology of 17 beta-hydroxysteroid dehydrogenase 3 deficiency.

Autosomal recessive mutations in the 17 beta-hydroxysteroid dehydrogenase 3 gene impair the formation of testosterone in the fetal testis and give rise to genetic males with female external genitalia. Such individuals are usually raised as females, but virilize at the time of expected puberty as the result of increases in serum testosterone. Here we describe mutations in 12 additional subjects/families with this disorder. The 14 mutations characterized to date include 10 missense mutations, 3 splice junction abnormalities, and 1 small deletion that results in a frame shift. Three of these mutations have occurred in more than 1 family. Complementary DNAs incorporating 9 of the 10 missense mutations have been constructed and expressed in reporter cells; 8 of the 9 missense mutations cause almost complete loss of enzymatic activity. In 2 subjects with loss of function, missense mutations testosterone levels in testicular venous blood were very low. Considered together, these findings strongly suggest that the common mechanism for testosterone formation in postpubertal subjects with this disorder is the conversion of circulating androstenedione to testosterone by one or more of the unaffected 17 beta-hydroxysteroid dehydrogenase isoenzymes.

17-Hydroxysteroid Dehydrogenases↗
PubMed1996

Effect of short-term fasting on free/dissociable insulin-like growth factor I concentrations in normal human serum.

A small portion of circulating insulin-like growth factor I (IGF-I) is detected in the free or readily dissociable state, which is thought to be the metabolically active form. The amount of free/dissociable IGF-I in serum is dependent on a complex interplay between the production rate and the concentrations of IGF-I and IGF-binding proteins (IGFBPs). IGF availability is also influenced by posttranslational changes in IGFBPs that affect the affinity of IGFBPs for IGF-I. In the present study, we examined whether a short term fast (approximately 12 h) alters the serum concentration of free/dissociable IGF-I, and whether these changes are associated with alterations in IGFBP-1 and the proteolysis status of IGFBP-3. Circulating free/dissociable IGF-I concentrations, as assessed by a two-site immunoradiometric assay, did not differ between fasting and 4 h after a morning meal (1.48 +/- 0.07 vs. 1.50 +/- 0.07 microgram/L, respectively). Likewise, free/dissociable IGF-I levels measured by RIA after separation by centrifugal ultrafiltration were not different between the two groups (1.43 +/- 0.14 vs. 1.38 +/- 0.18 microgram/L, respectively). IGF-I bioactivity, as measured by thymidine incorporation by fibroblasts, did not differ in fasting and 4-h postprandial sera. There was no difference in IGFBP-3 and total acid-ethanol-extractable IGF-I concentrations in serum from fasted and fed subjects. In contrast, the concentration of IGFBP-1 in the serum was increased approximately 5-fold in the fasted state compared to fed values. IGFBP-1 existed in a highly phosphorylated form under fasting conditions. There was no change in IGFBP-3 proteolysis assessed either in vivo or in vitro between the fasting and fed states. The results indicate that a physiologically relevant short term overnight fast does not alter the circulating levels of free/dissociable IGF-I despite a marked elevation in IGFBP-1.

Adult↗
PubMed1996

Safety of recombinant deoxyribonucleic acid-derived growth hormone: The National Cooperative Growth Study experience.

The National Cooperative Growth Study has monitored the safety of recombinant human GH (rhGH) since 1985. Data have been collected from more than 19,000 children representing over 47,000 patient-years of rhGH treatment. Children receiving GH for renal disease were more likely to develop problems such as intracranial hypertension than those with GH deficiency (P < 0.01). Children with idiopathic short stature were less likely to develop slipped capital femoral epiphysis than those with GH deficiency or Turner's syndrome (P < 0.01). There was no evidence of an increased recurrence of leukemia or central nervous system tumors. There were 3 new cases of leukemia in children without known risk factors for developing leukemia and 5 cases in children with known risk factors. Growth deceleration associated with high affinity, high capacity antibodies to GH was found in only 2 of 5039 subjects tested (0.04%). Major adverse events in association with rhGH treatment have been rare, and preexisting medical conditions such as renal insufficiency may affect their frequency.

Adolescent↗
PubMed1995

Complications of growth hormone therapy in children.

The introduction of human growth hormone (GH) prepared by recombinant DNA technology has resulted in increased numbers of children and adults receiving treatment. This trend has led to questions concerning the safety of GH, particularly when used for indications other than GH deficiency. This review discusses the effects of GH on fluid, lipid, and carbohydrate metabolism; the risk of intracranial hypertension or pseudotumor cerebri; the effects on the skeletal system; the risk of malignancy; and the effects on the immune system. At present, GH treatment appears to be safe, although long-term follow-up of GH-treated patients is necessary.

Adult↗
PubMed1995

Insulin-like growth factor-binding protein-2 and insulin: studies in children with type 1 diabetes mellitus and maturity-onset diabetes of the young.

The regulation of circulating insulin-like growth factor-binding protein-2 (IGFBP-2) in humans is not well understood. In vitro and animal data have identified the role of insulin in the regulation of IGFBP-2, but such a relationship has not been established clearly in humans. In the present study, serum IGFBP-2 concentrations were assessed by Western ligand blot and immunoblot analysis in children with newly diagnosed and untreated insulin-dependent diabetes mellitus (IDDM) and maturity-onset diabetes of the young before and at various times after insulin therapy. For comparison, IGFBP-2 levels were also determined in lean and obese age-matched controls. Children with IDDM were grouped according to their serum bicarbonate levels at the time of presentation (group A, > 20; group B, 13-20; group C, < 13 milliequivalents/L). Densitometric analysis demonstrated that before insulin therapy, group A patients had serum IGFBP-2 levels comparable to those in lean controls, and no significant change in IGFBP-2 was observed during insulin therapy. However, group B patients had a 2-fold elevation in IGFBP-2 levels before insulin therapy compared to lean controls. In these patients, IGFBP-2 tended to decrease at 1 week, but was not significantly reduced until 1 month after the initiation of insulin therapy. Group C patients had a 2.5-fold elevation of IGFBP-2 before treatment, which normalized by 1 month after treatment. Children with maturity-onset diabetes of the young, who had insulin levels and body mass indexes greater than IDDM patients and lean controls, had significantly lower IGFBP-2 levels than both lean and obese controls. IGFBP-2 levels tended to decrease further during insulin therapy. These results indicate that long standing alterations in serum insulin concentrations beyond the physiological range have significant influence on serum IGFBP-2 levels in children and confirm earlier findings that serum IGFBP-2 levels are not acutely regulated by insulin.

Blood Glucose↗
PubMed1995

Intestinal lymphangiectasia in a patient with autoimmune polyglandular disease type I and steatorrhea.

Steatorrhea is seen in 18-24% of patients with autoimmune polyglandular disease (APD) type 1. The etiology and pathophysiology of the steatorrhea in this disease are unknown. We present a patient with APD type 1 and steatorrhea in whom biopsies revealed intestinal lymphangiectasia. This association has not been previously described. Intestinal lymphangiectasia may explain the steatorrhea in some patients with ADP type 1. As blind intestinal biopsies may miss areas of intestinal lymphangiectasia, endoscopically directed intestinal biopsies should be included in the evaluation of steatorrhea in APD type 1.

Celiac Disease↗
PubMed1995

Effect of insulin on the insulin-like growth factor system in children with new-onset insulin-dependent diabetes mellitus.

To further characterize the mechanism of impaired growth in children with insulin-dependent diabetes mellitus, we examined the serum components of the insulin-like growth factor (IGF) system in 11 children with new-onset insulin-dependent diabetes mellitus and followed the effect of insulinization on the IGF system longitudinally 1 day, 1 week, and 1 month after starting insulin treatment. Before insulin therapy, serum IGF-I, IGF-II, IGF-binding protein-3 (IGFBP-3), and GH-binding protein (GHBP) levels were significantly decreased, whereas IGFBP-1 and cortisol were significantly increased in diabetic children compared to those in an age-, sex-, and stage of puberty-matched control group. Random serum GH concentrations did not differ significantly. The alterations in the IGF system reversed with insulin therapy in a sequential manner. IGFBP-1 fell rapidly and was comparable to control values within 24 h after insulin treatment. IGF-I rose 1 week after treatment, reaching levels comparable to those in controls and continued to rise through 1 month of treatment. IGF-II, IGFBP-3, and GHBP showed a slower pattern of change, with their levels reaching control values only 1 month after the start of insulin treatment. Improvement in glycemic control, as determined by a change in hemoglobin-A1c, correlated positively with improvement in IGF-I, IGF-II, IGFBP-3, GHBP, and weight gain after 1 month of insulin therapy. These data are consistent with the hypothesis that changes in the IGF system in the insulinopenic state are similar to those during nutritional deprivation and may serve to minimize IGF's anabolic actions. The decreases in IGF-I, IGF-II, and IGFBP-3 may in part be due to a decrease in the GHBP/receptor. However, the observation that an increase in serum IGF-I was observed earlier than an increase in GHBP and without a significant change in serum GH suggests a direct stimulatory effect of insulin on liver IGF-I production or reversal by insulin of some postreceptor defect in GH action independent of GHBP.

Adolescent↗
PubMed1995

Insulin-like growth factor binding protein-3 proteolysis in children with insulin-dependent diabetes mellitus: a possible role for insulin in the regulation of IGFBP-3 protease activity.

Limited proteolysis of serum insulin-like growth factor (IGF) binding protein (IGFBP)-3 has been described in various conditions and may increase the bioavailability of IGFs. The physiological regulators of serum IGFBP-3 protease activity are unknown. To characterize the relationship between insulin and IGFBP-3 protease activity, we have examined serum IGFBP-3 proteolysis in children with untreated insulin-dependent diabetes mellitus (IDDM) and have followed the effect of insulin therapy on serum IGFBP-3 proteolysis at 1 day, 1 week, and 1 month after the initiation of insulin therapy. Ligand blot analysis of sera from untreated children with IDDM showed that intact IGFBP-3 was 50 +/- 9% of the age-matched control pool. After the initiation of insulin treatment, IGFBP-3 did not change significantly at 1 day after treatment but increased dramatically at 1 week (90 +/- 13%) and 1 month after treatment (102 +/- 13%). In contrast, when measured by immunoradiometric assay (which detects both intact and fragments of IGFBP-3), IGFBP-3 levels were 70% of the control pool before insulin therapy and did not increase significantly until 1 month after treatment. Immunoblot analysis demonstrated that intact IGFBP-3 doublet was diminished to 41 +/- 7% of controls, whereas the major IGFBP-3 fragment (30 kDa) was increased in IDDM sera before insulin therapy. After insulin, intact IGFBP-3 increased and the 30-kDa fragment decreased to values comparable to those observed in controls. In vivo IGFBP-3 proteolysis, which implies preassay exposure of serum IGFBP-3 to proteases, was estimated by immunoblot analysis. IGFBP-3 proteolysis was increased before insulin therapy (160 +/- 9%) and decreased to 81 +/- 9% at 1 week and to 71 +/- 11% at 1 month after insulin treatment. Residual serum IGFBP-3 protease activity was estimated by a 125I-IGFBP-3 degradation assay. Serum IGFBP-3 protease activity increased significantly in untreated diabetics, compared with activity in controls (128 +/- 5% vs. 99 +/- 11%). During insulin therapy, serum IGFBP-3 protease activity decreased gradually to 91 +/- 5% of control values at 1 month. Molecular sizes of the IGFBP-3 proteolytic fragments (30 kDa, 24 kDa, and 19 kDa) and inhibition profile of IGFBP-3 protease were similar in IDDM and pregnancy sera, indicating that similar proteases (cation-dependent serine proteases) were active in both conditions. These results suggest an important role of insulin in the regulation of IGFBP-3 protease activity. Increased IGFBP-3 proteolysis in the sera of children with IDDM may serve to counteract the catabolic state induced by insulin deficiency.

Adolescent↗
PubMed1994

Circulating growth hormone isoforms in girls with Turner's syndrome.

To evaluate the presence of different GH isoforms in serum of girls with Turner's syndrome, we measured the serum GH content using RIAs with three different site-specific monoclonal antibodies (MAbs). We compared the results to those obtained with authentic GH and GH isoforms. Compared to pituitary GH (mol wt, 22K daltons) as the standard for all three MAbs, serum from girls with Turner's syndrome did not displace tracer [125I]GH equally with all three MAbs. The relative amounts of GH-immunoreactive material found in Turner's syndrome were different from the amounts observed in normal adults and most children with idiopathic short stature. The presence of GH, other than 22K GH, in serum from girls with Turner's syndrome was confirmed by affinity chromatography. The existence of different isoforms of GH, as shown by different cross-reactivity patterns with different MAbs to GH, may explain the conflicting results reported for GH secretion in girls with Turner's syndrome.

Adolescent↗
PubMed1993

DiGeorge anomaly with renal agenesis in infants of mothers with diabetes.

We report on 2 infants with the DiGeorge anomaly born to diabetic mothers treated with insulin. Both infants had unilateral renal agenesis. One of the mothers has manifestations suggestive of velo-cardio-facial syndrome (VCFS). Cytogenetic studies on both patients and the mother with apparent VCFS were normal. Molecular studies utilizing probes from the DiGeorge critical region did not demonstrate a 22q11 microdeletion in either patient or the mother with apparent VCFS. We conclude that maternal diabetes is a pathogenetic factor in the DiGeorge anomaly, and infants of diabetic mothers who have this anomaly should also be screened for renal agenesis.

Adult↗
PubMed1993

Factors predicting the response to growth hormone (GH) therapy in prepubertal children with GH deficiency.

To identify factors influencing the response to GH therapy, we used a multiple regression model to analyze data from 632 naive prepubertal children with GH deficiency (GHD). There were 523 children with idiopathic and 109 children with organic GHD. They were treated with the same preparation of biosynthetic methionyl GH (somatrem, Protropin) for at least 1 yr. In children with idiopathic GHD, six variables predicted 40% of the response to treatment. They were (listed in relative importance, all P < 0.0001): age, log maximum GH, weight adjusted for height, dosing schedule, dose, and midparental height. Three variables, pretreatment growth rate, log maximum GH, and age, predicted 20% of the GH response in children with organic GHD. When data for all children were analyzed using analysis of covariance, children with idiopathic GHD grew better than those with organic GHD (mean +/- SD, 9.2 +/- 2.4 vs. 8.8 +/- 2.6 cm/yr; P < 0.0001). The children (both organic and idiopathic GHD) who did not respond well to treatment were younger and thinner than those who did. Early diagnosis and initiation of therapy should be beneficial to ultimate height attainment. The best response to GH therapy should be in young children with severe idiopathic GHD who receive daily weight-adjusted doses. The use of GH daily in higher doses would be expected to be most beneficial in older children with acquired and/or less severe GHD or in children who are underweight for height.

Aging↗
PubMed1992

Identification of new markers in Xp21 between DXS28 (C7) and DMD.

Characterization of Xp21 distal to Duchenne muscular dystrophy (DMD) in the region containing the genes for adrenal hypoplasia congenita (AHC) and glycerol kinase deficiency (GKD) has been limited due to a paucity of probes. Two probes were localized between DXS28 (C7) and AHC, the yeast artificial chromosome insert YHX39 (DXS727) and the polymorphic phage clone QST59 (DXS319). A genomic clone, FT1 (DXS726), 3' to DMD, was also characterized. Portions of the three probes were sequenced and primer pairs were generated to amplify a sequence-tagged site within each probe. Amplification of DNA from patients confirmed the deletion results obtained by Southern blot analysis, and these three sequence-tagged sites were successfully combined for triplex PCR. In addition to facilitating molecular genetic diagnosis in Xp21, these probes can be used to identify additional YACs and other probes to further increase the genomic information and diagnostic capabilities in this region.

Base Sequence↗
PubMed1992

The role of adrenocorticotropin testing in evaluating girls with premature adrenarche and hirsutism/oligomenorrhea.

To identify biochemical predictors for future development of hirsutism and/or oligomenorrhea (H/O) in girls with premature adrenarche (PA), we performed dexamethasone-suppressed ACTH stimulation tests in girls with PA (n = 46), young women (n = 44) with H/O, and adult women (n = 31). Cortisol, androstenedione, dehydroepiandrosterone, and 17-hydroxyprogesterone were measured. Seven girls with PA (15%) and seven with H/O (16%) had evidence of nonclassical adrenal steroid biosynthetic defects [nonclassical congenital adrenal hyperplasia (NCAH)]. Twenty-five girls with PA (54%) and 28 girls with H/O (64%) had the moderately elevated 17-hydroxyprogesterone response to ACTH that has been reported in obligate heterozygotes for 21-hydroxylase deficiency. There were no clinical features that distinguished the girls with NCAH from the others. ACTH testing is an important tool in distinguishing those girls with PA and H/O who have NCAH. Although we could find no differences in other adrenal steroid hormones that might predict which of the other girls with PA might late develop H/O, black girls comprised a substantially smaller fraction of the population with H/O than of the population with PA (2% vs. 26%; chi 2 = 8.5; P less than 0.005). This observation suggests that PA, in blacks who do not have NCAH, is more likely to be a benign condition/than in other ethnic groups.

17-alpha-Hydroxyprogesterone↗
PubMed1991

Subacute thyroiditis presenting as Cushing's syndrome. Case report.

Subacute thyroiditis is a benign, self-limited disorder characterized by hyperthyroidism that resolves spontaneously. Although cortisol metabolism is accelerated in hyperthyroidism, cortisol levels are usually normal. We describe a child with subacute thyroiditis whose presenting complaints and preliminary evaluation suggested a diagnosis of Cushing's syndrome. There was spontaneous improvement in the signs and symptoms with concomitant normalization of laboratory values. We conclude that hypercortisolism may be a manifestation of hyperthyroidism, and the evaluation of Cushing's syndrome should include thyroid function tests.

Acute Disease↗