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.

<p>After telogen the follicle re-enters anagen and the dermal papilla reattaches to the base of the follicle.  If the old hair has not already epilated it will be pushed out by the new growing hair.</p>

<p>After telogen the follicle re-enters anagen and the dermal papilla reattaches to the base of the follicle.  If the old hair has not already epilated it will be pushed out by the new growing hair.</p>

===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 secondary seborrhea

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

===Specific changes associated with disease===

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

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

**Grossly: endocrine alopecia mainly over trunk and neck

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

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

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

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

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

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

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

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

*[[Pituitary Gland - Pathology#Pituitary_Hypofunction|'''GH deficiency (hyposomatotropism)''']] [[Image:Flame follicles.jpg|right|thumb|125px|<small><center>'''Flame Follicles'''. Courtesy of A. Jefferies</center></small>]]

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

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

*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

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

===='''Castration responsive dermatosis'''====

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

*Mainly involves intact male dogs

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

*Grossly: fluffy and wool like hair coat, symmetrical alopecia over perineum, thighs, ventral abdomen and thorax, neck; possible hyperpigmentation

*Microscopically: increased nmbe of catagen and telogen hair follicles and flame follicles

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

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

*Castration responsive dermatosis

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