Changes

The endocrine system typically has effects on the hair growth cycle so alopecia is a common finding.  Many types of endocrine skin disease cause similar pathology.   

The endocrine system typically has effects on the hair growth cycle so alopecia is a common finding.  Many types of endocrine skin disease cause similar pathology.   

Affects dogs more than any other species.

Affects dogs more than any other species.

===Pathogenesis===

===Pathogenesis===

<p>General skin changes ('''endocrine alopecia''') seen with endocrine disease include:

<p>General skin changes ('''endocrine alopecia''') seen with endocrine disease include:

*Hypotrichosis.

*[[Hypotrichosis]].

*Alopecia; usually bilaterally symmetric and non-pruritic.

*[[Alopecia]]; usually bilaterally symmetric and non-pruritic.

*Remaining coat is dry and dull

*Remaining coat is dry and dull

*Pigment disturbance.

*Pigment disturbance.

<p>Histologically many of the follicles will be in telogen where the haircoat is easily epilated and then fails to regrow.  This is why alopecia occurs over areas of friction (trunk face etc) while the legs and tail are spared.  Follicular and epidermal atrophy may be evident along with atrophy of the adnexa E.g sebaceous atrophy.</p>

<p>Histologically many of the follicles will be in telogen where the haircoat is easily epilated and then fails to regrow.  This is why alopecia occurs over areas of friction (trunk face etc) while the legs and tail are spared.  Follicular and epidermal atrophy may be evident along with atrophy of the adnexa E.g sebaceous atrophy.</p>

*Often complicated by [[Bacterial skin infections - Pathology|pyoderma]] or [[Skin Other - Pathology#Secondary seborrhea|secondary seborrhea]]

*Often complicated by [[Bacterial skin infections - Pathology|pyoderma]] or [[Seborrhea|secondary seborrhea]]

===Specific changes associated with disease===

===Specific changes associated with disease===

====[[Thyroid Gland - Pathology#Hypothyroidism|'''Hypothyroidism''']]====

====[[Hypothyroidism|'''Hypothyroidism''']]====

*Grossly: endocrine alopecia mainly over trunk and neck

*Grossly: endocrine alopecia mainly over trunk and neck

*Microscopically: endocrine alopecia plus mucin within the dermis -> myxoedema (dermal thickening), acanthotic epidermal and follicular infundibular epithelium

*Microscopically: endocrine alopecia plus mucin within the dermis -> myxoedema (dermal thickening), acanthotic epidermal and follicular infundibular epithelium

*Secondary pyoderma is common

*Secondary pyoderma is common

====[[Adrenal Glands - Pathology#Adrenal_Hyperfunction|'''Hyperadrenocorticism''']]====

====[[Hyperadrenocorticism|'''Hyperadrenocorticism''']]====

*Grossly: endocrine alopecia except on head and extremities, thin skin, comedones, easy bruising and poor wound healing, sometimes involves [[Adrenal Glands - Pathology#Pathophysiology_2|calcinosis cutis]]  

*Grossly: endocrine alopecia except on head and extremities, thin skin, comedones, easy bruising and poor wound healing, sometimes involves [[Hyperadrenocorticism#Pathophysiology|calcinosis cutis]]  

**In cats, skin is very easily torn

**In cats, skin is very easily torn

*Microscopically: epidermal, dermal and follicular atrophy, comedones, calcinosis cutis often with granulomatous inflammation and epidermal hyperplasia

*Microscopically: epidermal, dermal and follicular atrophy, comedones, calcinosis cutis often with granulomatous inflammation and epidermal hyperplasia

====[[Pituitary Gland - Pathology#Pituitary_Hypofunction|'''GH deficiency (hyposomatotropism)''']]====  

===='''GH deficiency (hyposomatotropism)'''====  

[[Image:Flame follicles.jpg|right|thumb|125px|<small><center>'''Flame Follicles'''. Courtesy of A. Jefferies</center></small>]]

[[Image:Flame follicles.jpg|right|thumb|125px|<small><center>'''Flame Follicles'''. Courtesy of A. Jefferies</center></small>]]

*Retained puppy hair coat, endocrine alopecia, decreased dermal elastin and catagen follicles ('''Flame follicles''').

*Retained puppy hair coat, endocrine alopecia, decreased dermal elastin and catagen follicles ('''Flame follicles''').

====[[Pituitary Gland - Pathology#Pituitary_Hyperfunction|'''Excess GH (hypersomatotropism)''']]====

===='''Excess GH ([[hypersomatotropism]])'''====

*Grossly: thick, folded skin on head, neck and extremities, possibly with hypertrichosis

*Grossly: thick, folded skin on head, neck and extremities, possibly with hypertrichosis

*Microscopically: epidermal hyperplasia, dermal fibrosis, mucinous degeneration of dermis

*Microscopically: epidermal hyperplasia, dermal fibrosis, mucinous degeneration of dermis

====[[Sex hormones - Pathology#Hyperoestrogenism|'''Hyperoestrogenism''']]====

====[[Hyperoestrogenism - Dog|'''Hyperoestrogenism''']]====

*Grossly: endocrine alopecia, enlarged vulva and abnormal oestrus cycle in females, gynecomastia, pendulous prepuce or enlarged prostate in males

*Grossly: endocrine alopecia, enlarged vulva and abnormal oestrus cycle in females, gynecomastia, pendulous prepuce or enlarged prostate in males

*Microscopically: telogen follicles, hyperkeratosis and acanthosis or epidermis and follicular infundibulum

*Microscopically: telogen follicles, hyperkeratosis and acanthosis or epidermis and follicular infundibulum

*Castration may temporarily remove symptoms  

*Castration may temporarily remove symptoms  

===='''Superficial necrolytic dermatopathy'''====

===='''[[Superficial Necrolytic Dermatopathy]]'''====

 

*Also known as ''diabetic dermatopathy, hepatocutaneous syndrome''

*Also known as ''diabetic dermatopathy, hepatocutaneous syndrome''

*In older dogs with diabetes mellitus, hepatic dysfunction or pancreatic lesions

*In older dogs with [[DM|diabetes mellitus]], hepatic dysfunction or pancreatic lesions

*Grossly: scaling and crusting, erythema, facial, genital and distal extremities alopecia, crusting, fissures and ulceration of foot pads

*Grossly: scaling and crusting, erythema, facial, genital and distal extremities alopecia, crusting, fissures and ulceration of foot pads

*Microscopically: trilaminar thickening of epidermis (outermost layer is keratotic, intermediate oedematous and vacuolated, inner is hyperplastic)

*Microscopically: trilaminar thickening of epidermis (outermost layer is keratotic, intermediate oedematous and vacuolated, inner is hyperplastic)