Sex Hormone and Endocrine Look-alike Dermatoses

Chapter 51 Sex Hormone and Endocrine Look-alike Dermatoses



Linda A. Frank




Key Point


Bilaterally symmetrical alopecia sparing the head and extremities is usually associated with an endocrine cause such as hypothyroidism or hyperadrenocorticism; however, this same pattern of alopecia is seen with sex hormone dermatoses and various other dermatoses described in this chapter.


The differential diagnoses for an “endocrine” pattern of alopecia (other than hypothyroidism and hyperadrenocorticism) include sex hormone aberrations, follicular arrest (Alopecia X), cyclic flank alopecia, pattern baldness, and post-clipping alopecia. In addition, more generalized non-inflammatory alopecias may be associated with follicular dysplasias and telogen defluxion.



Sex Hormone Dermatoses



Etiology


Sex hormones are produced primarily from cholesterol by the zona reticularis of the adrenal cortex and by the gonads. Sex hormones are also produced in the tissues by peripheral conversion. Sex hormone dermatoses are uncommon in the dog and are attributed to an overproduction of one or more of the sex hormones. This overproduction may arise endogenously from the adrenal glands or gonads or exogenously from administration of a hormone product. The alopecia results from the effects of hormones on the hair follicle, inhibiting the normal cyclic pattern of hair growth.



Hyperestrogenism



• The source of excess estrogen production is from cystic ovaries, ovarian granulosa cell tumors, or testicular tumors (especially Sertoli cell tumors). Iatrogenic estrogen supplementation (such as for treating urinary incontinence) can also be a source.

• Estrogen inhibits initiation of anagen, the hair growth phase.


Hyperandrogenism



• The source of excess androgen production is from testicular tumors (e.g., interstitial cell tumors, seminomas) and possibly from adrenal tumors.

• Hyperandrogenism is uncommonly associated with alopecia in dogs. Excess androgen is more often associated with hyperplasia and hypersecretion of the sebaceous and circumanal or hepatoid glands.


Hyperprogesteronism



• An endocrine pattern of alopecia caused by a progesterone-secreting Sertoli cell tumor was reported in one dog.

• Progesterone may bind to glucocorticoid receptors, thus blocking hair growth.

• Progesterone may also cross with testosterone receptors, resulting in either down-regulation or upregulation of the receptors.


Clinical Signs




Key Point


The classic endocrine pattern of alopecia is a bilaterally symmetrical diffuse alopecia sparing the head and extremities caused by non-inflammatory endocrine dermatoses. Focal or patchy alopecias are more likely caused by inflammatory dermatoses, such as pyoderma, demodicosis, or dermatophytosis.



Hyperestrogenism



Cutaneous Signs



• These dogs often present with bilaterally symmetrical alopecia sparing the head and extremities. The alopecia may begin in the perineal, inguinal, and flank regions and then progress to involve the entire trunk.

• Comedones may be seen in the inguinal region.

• The coat may have a generalized dry or oily seborrhea.

• Hyperpigmentation may be seen as diffuse pigmentation in the areas of alopecia, or it may appear as macular lesions with a ventral distribution.

• In male dogs, a clinical sign highly suggestive of excess estrogen production is linear preputial dermatosis that appears as a narrow strip of hyperpigmentation along the ventral midline from the prepuce toward the scrotum.


Female Reproductive Signs



• The nipples and vulva may be enlarged, similar to a normal heat cycle.

• The heat cycles may be abnormal, especially persistent or irregular estrus.


Male Reproductive Signs



• The testes may be palpably abnormal.

• The nipples may enlarge, similar to what occurs in females.

• Males may attract other male dogs.


Other Signs



• Hyperestrogenism can cause serious bone marrow suppression and aplastic anemia.


Hyperandrogenism



• Intact male dogs are most commonly affected. Testes are palpably normal in most cases, but a testicular tumor may be identified.

• Hyperandrogenism is only rarely associated with alopecia.

• Typical lesions include perianal gland hyperplasia, resulting in a “donut” ring around the anus. This can result in anal sac impaction.

• Generalized seborrhea oleosa is a presenting sign in some dogs.

• Local hyperplasia of the supracaudal gland may appear as alopecia and seborrhea of the dorsal aspect of the tail approximately one-third the distance from the tail base.


Hyperprogesteronism



• Bilaterally symmetrical alopecia sparing the head and extremities has been attributed to elevated progesterone in one dog.


Diagnosis


Suspect sex hormone dermatoses in dogs that have typical clinical signs after routine diagnostic testing has ruled out the more common causes of endocrine alopecia, such as hypothyroidism or hyperadrenocorticism (see Chapters 31 and 33). In intact dogs, the resolution of clinical signs in response to neutering confirms the diagnosis. In neutered dogs with sex hormone dermatosis, adrenal testing is required.



Diagnosis of Gonadal Causes in Intact Dogs



• In intact animals, the excess sex hormone is most likely gonadal in origin. Measure baseline concentrations of estradiol, progesterone, and testosterone to establish a presumptive diagnosis. If any of these hormones is substantially increased out of the normal range, then there is good reason to suspect this is causing the dermatosis.

• Use diagnostic imaging, especially ultrasonography, to identify gonadal tumors.

• Evaluate a complete blood count to assess bone marrow status when hyperestrogenism is suspected.

• Confirm the diagnosis based on resolution of clinical signs in response to neutering or ovariohysterectomy.

• The intact animal may also respond to treatment with an antagonistic hormone, such as androgen to treat hyperestrogenism; however, this approach is not recommended since the primary cause of the sex hormone imbalance is a gonadal tumor.


Diagnosis of Adrenal Tumors



• Adrenal tumors have been associated with abnormal sex hormone production; thus, in neutered dogs with clinical signs suggestive of a sex hormone dermatosis, the excess sex hormones are most likely arising from the adrenal glands.

• Perform abdominal ultrasonography to identify adrenal tumors.

• Measure the serum concentration of the sex hormones as well as cortisol, before and after adrenocorticotropic hormone (ACTH) stimulation, to identify substantial increases in one or more of these adrenal hormones. Hyperandrogenism sometimes occurs concurrently with hypercortisolemia. To perform the ACTH stimulation test, obtain baseline and, 1 hour post-ACTH, serum samples. ACTH is administered at 5μg/kg IV. The serum samples need to be frozen and mailed overnight to the following address: Clinical Endocrinology Service, 2407 River Drive, Rm A105 Veterinary Teaching Hospital, University of Tennessee, Knoxville, TN 37996-4543 (telephone: 865-974-5638).


Skin Biopsy


A skin biopsy may support the diagnosis of a sex hormone imbalance; however, the findings are nonspecific. The biopsy can only document the presence of a non-inflammatory alopecia accompanied by hairs that are not cycling (typical endocrine histopathology pattern). This is not specific for endocrine disease; it also is seen in many of the endocrine “look-alike” alopecias discussed in the later sections of this chapter.




Key Point


A biopsy result indicating an endocrine pattern of alopecia simply means that there is no inflammation to explain the alopecia, the thickness of the dermis and epidermis is normal to decreased, and the hairs are in telogen phase (not cycling). Think of this as a non-inflammatory pattern of alopecia that can be associated with endocrine or endocrine look-alike dermatoses rather than strictly an endocrine pattern of alopecia.

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Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Sex Hormone and Endocrine Look-alike Dermatoses

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