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Biomedical subjects

L M Crapo

Publications and source records attributed to L M Crapo.

12 recordsLinked to original sources
PubMed1999

Clinical and metabolic features of thyrotoxic periodic paralysis in 24 episodes.

BACKGROUND: Hypokalemia is a well-known, consistent finding in thyrotoxic periodic paralysis (TPP). It is less well known that hypophosphatemia and mild hypomagnesemia are often present in TPP and that rebound hyperkalemia can occur as a result of potassium therapy. OBJECTIVE: To report the prevalence of these electrolyte abnormalities in 24 episodes of TPP in 19 patients admitted to a single university-affiliated public hospital during a 15-year period. METHODS: The medical records of all patients admitted to the Santa Clara Valley Medical Center in San Jose, Calif, between August 1, 1982, and June 1, 1997, with any type of hypokalemic periodic paralysis were reviewed. In patients with TPP, serum potassium, phosphorus, and magnesium levels were evaluated during and after episodes of paralysis. The administered dose of potassium chloride, recovery time from hypokalemia, and prevalence of rebound hyperkalemia after recovery were also ascertained. Data are presented as mean +/- SD. RESULTS: Hypokalemia was present in all 24 initial episodes of TPP, with serum potassium levels ranging from 1.1 to 3.4 mmol/L (mean, 1.9+/-0.5 mmol/L). After recovery from hypokalemia, the maximum serum potassium level significantly increased, ranging from 4.0 to 6.6 mmol/L (mean, 4.9+/-0.5 mmol/L; P<.001). In 10 (42%) of 24 episodes, rebound hyperkalemia (serum potassium level >5.0 mmol/L) was present. Recovery time did not correlate with the potassium chloride dose administered (r = 0.17). Initial serum phosphorus levels ranged from 0.36 to 0.97 mmol/L (mean, 0.61+/-0.23 mmol/L) (1.1-3.0 mg/dL [mean, 1.9+/-0.7 mg/dL]), with hypophosphatemia present in 12 (80%) of 15 episodes. Serum phosphorus levels significantly increased (P<.01), to 1.26 to 1.74 mmol/L (mean, 1.48+/-0.16 mmol/L) (3.9-5.4 mg/dL [mean, 4.6+/-0.5 mg/dL]), with or without phosphorus replacement therapy. A slight increase in serum magnesium levels after paralysis resolved was observed in all patients (P<.07). No further episodes of paralysis occurred in any patients after they became euthyroid. CONCLUSIONS: Hypokalemia, hypophosphatemia, and mild hypomagnesemia are characteristic features of TPP. Hypokalemia occurred in 100% and hypophosphatemia in 80% of the episodes in our study. Rebound hyperkalemia is a potential hazard of potassium administration and occurred in 42% of 24 episodes.

Adult↗
PubMed1997

The epidemiology of thyroid disease and implications for screening.

The burden of thyroid disease in the general population is enormous. As many as 50% of people in the community have microscopic nodules, 3.5% have occult papillary carcinoma, 15% have palpable goiters, 10% demonstrate an abnormal thyroid-stimulating hormone level, and 5% of women have overt hypothyroidism or hyperthyroidism. Despite this high prevalence of thyroid disease, screening for these disorders is not recommended by any major health agency. This article explores the epidemiologic issues surrounding this complex problem by analyzing prevalence, incidence, and mortality data from a worldwide variety of sources.

Adult↗
PubMed1992

Protracted phencyclidine coma from an intestinal deposit.

Phencyclidine is a common drug of abuse that can be taken orally, intravenously, or by inhalation. We describe a massive overdose of phencyclidine in a patient who swallowed a plastic bag containing the drug. Quantitative serum phencyclidine levels remained persistently elevated for several weeks. On hospital day 20, a plastic bag was passed via the rectum. Subsequently, the patient's serum phencyclidine levels fell in accordance with previously described pharmacokinetics. The patient rapidly recovered neurologic function. Persistently elevated serum drug levels should suggest continued drug absorption from a gastrointestinal deposit. We propose that colonoscopy and esophagogastroduodenoscopy be performed early in this setting.

Adult↗
PubMed1990

Monitoring therapy in patients taking levothyroxine.

PURPOSE: To evaluate the use of thyroid function tests to monitor therapy in patients taking levothyroxine. DATA IDENTIFICATION: Studies published between 1966 and January 1990 were identified through computer searches and references of identified studies. STUDY SELECTION: Studies that included a careful description of the patients under study, well-defined interventions, and a meaningful criterion standard were emphasized. DATA EXTRACTION: Data from different studies were combined to estimate the probability of positive and negative test results in well-defined clinical situations. Informal methods of synthesizing evidence were used when combining data from different studies was not justified. RESULTS: The sensitive thyrotropin (TSH) test is the preferred method to monitor therapy because it agrees with physiologic measures of thyroid hormone effect. Among clinically euthyroid patients who take 100 to 150 micrograms/d of levothyroxine, the probability that the sensitive thyrotropin will be undetectable is close to 50%. These patients are most likely to benefit from testing. Patients who take over 250 micrograms/d are almost certain to have undetectable sensitive thyrotropin levels; in these patients, the dose may be lowered without testing. CONCLUSIONS: Adequate long-term studies are needed to determine the role of biochemical testing in monitoring therapy. Current evidence suggests that the sensitive thyrotropin test should be used to monitor therapy. Clinically euthyroid patients taking lower dosages of levothyroxine are most likely to benefit from testing.

Humans↗
PubMed1990

Screening for thyroid disease.

PURPOSE: To evaluate the usefulness of screening for thyroid dysfunction in various clinical settings. DESIGN: Review and synthesis of the literature. MAIN RESULTS: Screening in the community detects new overt thyrotoxicosis or hypothyroidism in approximately 0.5% of the general population. The yield is best among women over 40 years of age (1%) and is lowest among young men (0%). Case-finding (testing clinic patients who are seeing a physician for unrelated reasons) has a better yield and is less expensive than screening in the community. Patients hospitalized with acute illnesses do not benefit from routine thyroid function testing. However, patients who are admitted to specialized geriatric units because of general disability, failure to thrive, and other indications may benefit. In various studies, from 2% to 5% of patients admitted to geriatric units have treatable thyroid disease. The serum total thyroxine, free thyroxine index, free thyroxine, and sensitive thyrotropin assay are all effective as initial tests for screening. The sensitive thyrotropin assay is less cost-effective than the other choices. RECOMMENDATIONS: Case-finding in some women over 40 years of age can be useful. Patients admitted to specialized geriatric units may also benefit from routine testing. Thyroid function tests are not indicated for community screening programs or for patients hospitalized with acute medical or psychiatric illnesses.

Adult↗
PubMed1983

Optimal therapy for the geriatric patient: the challenge to clinical pharmacology.

The elderly are an increasing proportion of the population. Their median life span should rise to 85 years, although in later life organs of drug distribution and elimination may deteriorate in function and 100 years will remain the general maximum. Progressive containment of chronic diseases will still leave them at lethal risk from acute infectious diseases because of depleted homeostatic reserves of vital systems (cardiovascular, hepatic, immunological and renal). A decline in chronic disease should lengthen the period of well-being and reduce medical needs and perhaps drug needs of older persons. To estimate further therapeutic requirements of the elderly, information is needed on the epidemiology of drug use and rates of efficacy and toxicity in the elderly. Implicit in the data gathering is a true need for systematic post-marketing surveillance (PMS) of drugs with particular respect to drug efficacy and unanticipated adverse or beneficial reactions in this age group. Observational, non-experimental techniques can be devised and should be tested as appropriate methods of establishing the rates of anticipated efficacy and unwanted effects of drugs. The application of such techniques may be one of the only feasible ways to establish utility functions for drugs used in the elderly.

Aged↗
PubMed1979

Insulin and the phosphorylation of intracellular proteins.

Protein phosphorylation is a ubiquitous form of posttranslational protein modification in mammalian cells which often serves to regulate protein function. Insulin alters the activity of a number of enzymes known to be regulated via phosphorylation. With the premise that altered protein phosphorylation might be an obligatory intermediate step in insulin action, we have examined the effects of insulin on the phosphorylation of the major phosphopeptides in adipocytes and hepatocytes. Insulin affects overall protein phosphorylation in two ways: 1) Insulin selectively stimulates the phosphorylation of a major peptide in adipose tissue (MW 123,000) and liver (MW 46,000) through a mechanism independent of cAMP and the cAMP-dependent protein kinase. Net dephosphorylation is not observed with insulin as the sole hormone. 2) Insulin antagonizes cAMP-directed protein phosphorylation. The mechanism of insulin-stimulated phosphorylation and the possible role of this phenomenon in overall insulin action is discussed.

Adipose Tissue↗
PubMed1976

Regulation of plasma membrane protein phosphorylation in two mammalian cell types.

The appreciation of protein phosphorylation as a ubiquitous mechanism for the post-translational control of protein function has drawn our attention to the phosphorylation of plasma membrane proteins. We have studied this phenomenon in the human erythrocyte and rat adipocyte, and have observed several features, common to the two systems, which may be of general significance. In examining protein phosphorylation in intact cells incubated with 32Pi, it is evident that the 32P-polypeptides of the plasma membrane are among the most highly labelled species in the cell, despite their minor contribution to overall protein content. The addition of epinephrine (to adipocytes) or cAMP (to erythrocytes) increases the phosphorylation of certain peptides, whereas others are unaffected. The protein kinases mediating these phosphorylations are present in the plasma membrane as isolated, and can be divided into two groups--cAMP dependent and cAMP independent. These two classes of kinase differ markedly in their substrate specificity toward endogenous and exogenous polypeptide substrates. Two classes of protein kinases with similar properties can be detected in the cytoplasm. The relationship between the membrane-bound and cytoplasmic enzymes is uncertain. The potential roles of the plasma membrane cAMP dependent protein kinases are evident from the diverse effects of cAMP on surface properties; however, the prevalence of plasma membrane proteins phosphorylated via cAMP independent pathways is striking. Thus, elucidation of the regulatory properties of the plasma membrane cAMP independent protein kinases may give new insight into the control of a variety of surface phenomena not mediated by cAMP.

Adipose Tissue↗