Analysis of genetic polymorphisms of steroid 5alpha-reductase type 1 and 2 genes in Korean men with androgenetic alopecia

Clinical biochemistry of dihydrotestosterone

Dihydrotestosterone (DHT) is the most potent natural androgen in humans. There has been an increasing interest in this androgen and its role in the development of primary and secondary sexual characteristics as well as its potential roles in diseases ranging from prostate and breast cancer to Alzheimer's disease. Despite the range of pathologies shown to involve DHT there is little evidence for measurement of serum DHT in the management of these diseases. In this review we describe the physiology of DHT production and action, summarize current concepts in the role of DHT in the pathogenesis of various disorders of sexual development, compare current methods for the measurement of DHT and conclude on the clinical utility of DHT measurement. The clinical indications for the measurement of DHT in serum are: investigation of 5α reductase deficiency in infants with ambiguous genitalia and palpable gonads; men with delayed puberty and/or undescended testes; and to confirm the presence of active testicular tissue. Investigation is aided by the use of human chorionic gonadotrophin stimulation. Due to paucity of published data on this procedure, it is important to follow guidelines prescribed by the laboratory performing the analysis to ensure accurate interpretation.

5α-Reduced glucocorticoids: a story of natural selection

5α-Reduced glucocorticoids (GCs) are formed when one of the two isozymes of 5α-reductase reduces the Δ(4-5) double bond in the A-ring of GCs. These steroids are largely viewed inert, despite the acceptance that other 5α-dihydro steroids, e.g. 5α-dihydrotestosterone, retain or have increased activity at their cognate receptors. However, recent findings suggest that 5α-reduced metabolites of corticosterone have dissociated actions on GC receptors (GRs) in vivo and in vitro and are thus potential candidates for safer anti-inflammatory steroids. 5α-Dihydro- and 5α-tetrahydro-corticosterone can bind with GRs, but interest in these compounds had been limited, since they only weakly activated metabolic gene transcription. However, a greater understanding of the signalling mechanisms has revealed that transactivation represents only one mode of signalling via the GR and recently the abilities of 5α-reduced GCs to suppress inflammation have been demonstrated in vitro and in vivo. Thus, the balance of parent GC and its 5α-reduced metabolite may critically affect the profile of GR signalling. 5α-Reduction of GCs is up-regulated in liver in metabolic disease and may represent a pathway that protects from both GC-induced fuel dyshomeostasis and concomitant inflammatory insult. Therefore, 5α-reduced steroids provide hope for drug development, but may also act as biomarkers of the inflammatory status of the liver in metabolic disease. With these proposals in mind, careful attention must be paid to the possible adverse metabolic effects of 5α-reductase inhibitors, drugs that are commonly administered long term for the treatment of benign prostatic hyperplasia.

Hormonal regulation of hair follicles exhibits a biological paradox

Hair's importance for insulation and camouflage or human communication means that hairs need to change with season, age or sexual development. Regular, regenerating hair follicle growth cycles produce new hairs which may differ in colour and/or size, e.g., beard development. Hormones of the pineal-hypothalamus-pituitary axis coordinate seasonal changes, while androgens regulate most sexual aspects with paradoxically different effects depending on body site; compare beard growth and balding! Hormones affect follicular mesenchymal-epithelial interactions altering growing time, dermal papilla size and dermal papilla cell, keratinocyte and melanocyte activity. Greater understanding of these mechanisms should improve treatments for poorly controlled hair disorders, alopecia and hirsutism.

[Androgenetic alopecia]

Androgenetic alopecia is the most common form of hair loss in men and women. Although the clinical manifestations are different in men and women, the pathogenetic pathways leading to this type of hair loss are similar in both sexes. In short genetically predestined hair follicles show an increased sensitivity to androgens. In recent years, much new data concerning the pathophysiology, management and therapy of androgenetic alopecia has been gathered. This article gives a critical overview of these new findings and assesses their practical relevance.