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Related Concept Videos

Asthma: Pathogenesis and Management01:20

Asthma: Pathogenesis and Management

Asthma is a chronic pulmonary condition involving inflammation of the airways, hyper-reactivity, and reversible obstruction of the airways. This condition can significantly impact a person's quality of life, making breathing difficult and leading to distressing symptoms.
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Chronic Obstructive Pulmonary Disease-II: Pathophysiology01:20

Chronic Obstructive Pulmonary Disease-II: Pathophysiology

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Chronic Inflammation
Asthma-II: Pathophysiology and Classification01:26

Asthma-II: Pathophysiology and Classification

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Asthma I: Introduction01:28

Asthma I: Introduction

Asthma is a chronic inflammatory disorder of the airways characterized by variable airflow obstruction and heightened bronchial responsiveness to a wide range of triggers. The underlying inflammation leads to airway swelling, mucus hypersecretion, and smooth muscle constriction, all of which narrow the airway lumen and impede airflow. Clinically, asthma presents with recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing, symptoms that typically vary in intensity and...
Chronic Obstructive Pulmonary Disease I: Introduction01:23

Chronic Obstructive Pulmonary Disease I: Introduction

Chronic obstructive pulmonary disease is a common, preventable, and treatable respiratory disorder characterized by persistent symptoms and progressive airflow limitation. This limitation results from a combination of small-airway disease (obstructive bronchiolitis) and parenchymal destruction (emphysema), both driven by chronic inflammation from exposure to harmful particles or gases.The disease includes two main pathological entities: emphysema, marked by destruction of alveolar walls and...
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Chronic bronchitis is a key phenotype of chronic obstructive pulmonary disease (COPD), characterized by airway-centered inflammation and mucus overproduction. It develops from long-term exposure to harmful particles or gases, most commonly cigarette smoke, which triggers a persistent inflammatory response.Cellular and Structural ChangesInflammation initially affects the large bronchi and later the smaller airways, with infiltration by immune cells, including neutrophils, macrophages, and...

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Frontal fibrosing alopecia sparing a dermal melanocytic nevus: a report of two cases of Renbök phenomenon.

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Related Experiment Video

Updated: Jul 5, 2026

A New Technique for Quantitative Analysis of Hair Loss in Mice Using Grayscale Analysis
06:41

A New Technique for Quantitative Analysis of Hair Loss in Mice Using Grayscale Analysis

Published on: March 9, 2015

Current understanding of androgenetic alopecia. Part I: etiopathogenesis.

R Hoffmann1, R Happle

  • 1Department of Dermatology, Philipp University, Deutschhausstr. 9, D-35033 Marburg, Germany.

European Journal of Dermatology : EJD
|June 10, 2000
PubMed
Summary
This summary is machine-generated.

Androgenetic alopecia (AGA) is common hair loss driven by genetics. The enzyme 5a-reductase converts testosterone to DHT, causing hair follicle miniaturization in AGA.

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Last Updated: Jul 5, 2026

A New Technique for Quantitative Analysis of Hair Loss in Mice Using Grayscale Analysis
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Published on: March 9, 2015

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09:29

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Published on: May 13, 2020

Area of Science:

  • Dermatology
  • Genetics
  • Endocrinology

Background:

  • Androgenetic alopecia (AGA) is the most prevalent form of hair loss affecting both men and women.
  • AGA is a genetically predisposed condition characterized by a patterned, continuous hair loss process.
  • The genetic basis is likely polygenic, as simple Mendelian inheritance does not fully explain familial patterns.

Purpose of the Study:

  • To elucidate the pathogenetic steps involved in androgenetic alopecia.
  • To understand the role of specific enzymes in the development of AGA.
  • To clarify the molecular mechanisms underlying DHT-dependent hair loss.

Main Methods:

  • Review of recent experimental and clinical advances in understanding AGA.
  • Focus on the role of steroidogenic isoenzymes, particularly type 2 5a-reductase.
  • Analysis of the intrafollicular conversion of testosterone (T) to dihydrotestosterone (DHT).

Main Results:

  • AGA is a dihydrotestosterone (DHT)-dependent process.
  • DHT causes continuous miniaturization of sensitive hair follicles (HF).
  • Type 2 5a-reductase in the dermal papilla is crucial for converting T to DHT within the hair follicle.

Conclusions:

  • The type 2 5a-reductase enzyme plays a central role in the pathogenesis of androgenetic alopecia.
  • Understanding the intrafollicular conversion of testosterone to DHT is key to explaining AGA.
  • Further research into molecular steps can advance treatments for this common hair loss condition.