Seasonal Shedding and Hormonal Balance in Dogs

Twice a year, many double‑coated dogs quietly do something astonishing: they can lose the equivalent of their entire undercoat in just 2–3 weeks. In one report on female German Shepherds, weekly hair loss jumped from about 5 grams to around 70 grams just before their heat cycle – a more than tenfold increase in shedding, driven not by “being a messy dog,” but by hormones shifting in response to seasons and reproductive status [1].

If you’ve ever stood in a cloud of fur wondering what on earth is going on with your dog’s coat, there is a real, biologically tidy story underneath the chaos. It involves daylight, hormones, genetics, stress, and the quiet tug‑of‑war between “nature’s outdoor dog” and “our indoor family member.”

This article is about that story – and about how to tell when shedding is simply your dog’s biology doing its job, and when it might be a flag for something deeper.

Why dogs shed more in some seasons – and why it’s not just about temperature

We often blame the weather: “It’s warming up, so she’s dropping her winter coat.” Temperature matters, but for dogs, daylight length (photoperiod) is the main conductor of the shedding orchestra.

Light hits the retina → signals travel to the brain → the brain adjusts hormone release (including melatonin and hormones that influence thyroid and sex hormones) → hair follicles change their behavior.

Research and clinical experience show:

• Seasonal peaks: Shedding tends to spike in spring and fall, especially in double‑coated breeds, driven largely by changes in daylight rather than just the thermometer [2][3][4][9][10].

• Outdoor vs indoor dogs: Dogs who spend more time in natural light often show clearer, more dramatic “blowing coat” events. Indoor dogs under artificial light and constant temperatures may shed more moderately, all year, with less obvious peaks [4].

• Typical time frame: A major seasonal shed usually lasts about 2–3 weeks during transition months for many double‑coated dogs [9][11].

So if your dog seems to explode in fur every April and October, that’s not a personal failing in housekeeping. It’s their endocrine system responding to the sky.

Coat types: why some dogs “blow coat” and others just… don’t

Understanding your dog’s coat type is one of the simplest ways to decode their shedding.

Double coat vs single coat

• Double‑coated breedsExamples: Huskies, German Shepherds, Golden Retrievers, Border Collies.Structure:

  • Guard hairs: The longer, stiffer outer layer.

  • Undercoat: Dense, soft, insulating layer that is heavily shed seasonally.

  These dogs often “blow coat” – a term for the intense, short‑lived shedding events in spring and fall where the undercoat comes out in clumps or thick tufts.

  
  

• Single‑coated breedsExamples: Poodles, Dachshunds, many terriers.Structure:

  • Lacking a dense undercoat. Hair may grow continuously and be trimmed (like Poodles), or shed lightly but fairly evenly year‑round.

  These dogs tend to have less dramatic seasonal swings, though they still follow the same basic hair growth cycle.

  
  

Genetics and “low‑shedding” dogs

Shedding is influenced by multiple genes. One example is MC5R, a gene associated with sebum production and coat characteristics; some “unfurnished” dogs with certain alleles tend to shed less seasonally [7]. Breeders sometimes select for these traits in “low‑shedding” lines.

Important nuance: “Low‑shedding” is not “no shedding,” and less fur on the couch does not mean fewer hormones at work. The underlying cycles are still there – they just show up differently.

The hair growth cycle: what hormones actually do to hair follicles

Every hair on your dog’s body is going through a repeating cycle:

1. Anagen – growth phaseThe hair is actively growing. Hormones like thyroid hormones support this phase.

2. Catagen – transition phaseGrowth slows and the follicle begins to shrink.

3. Telogen – resting phaseThe hair is no longer growing but stays anchored in the follicle.

4. Exogen – shedding phaseThe hair is released and falls out (or is brushed out, or deposited neatly on your black pants).

Hormones modulate how long each phase lasts and how many follicles are in each stage at a given time. When a lot of follicles shift into exogen together, you see a “shed.”

Key hormonal influences:

• Thyroid hormones: Help regulate metabolism and hair growth. Low thyroid (hypothyroidism) often leads to dull coats, thinning hair, and abnormal shedding or bald patches [5][11][14].

• Sex hormones (estrogen, progesterone, testosterone): Influence coat density and shedding around heat cycles, pregnancy, and neutering/spaying.Example: In that German Shepherd report, shedding increased from ~5 g to ~70 g weekly just before estrus (heat) [1].

• Stress hormones (like cortisol): Affect hair cycling and can alter when hairs enter or leave the growth phases. A study measuring hair cortisol concentrations (HCC) found seasonal variation, with higher levels in winter, especially in females [12] – linking stress, seasons, and what happens in the coat.

• Photoperiod‑related hormones: Daylight modulates hormones that indirectly affect the hair cycle (via the brain and endocrine glands). Studies cited by NIH work show photoperiod is a major driver of seasonal coat changes [3].

You don’t see hormones, but you do see their footprints: the texture, shine, thickness, and timing of your dog’s shedding.

Life stages and hormones: why your dog’s coat changes over time

Hormonal balance isn’t static. It shifts with age, reproductive status, and health – and the coat often tells the story first.

Puppy to adult: the first big transition

• Puppies often have a softer, fluffier coat that changes as they mature.

• As sex hormones and thyroid function mature, the “adult coat” may become:

  • Thicker or coarser

  • A different shade or pattern

  • More or less prone to shedding

This transition can involve a noticeable shed and sometimes worries owners who weren’t expecting it.

Heat cycles, pregnancy, and nursing

For intact females:

• Before and after heat (estrus)

  As shown in German Shepherds, shedding can spike dramatically around heat cycles [1]. That’s hormone‑driven, not a sign of poor care.

  
  

• Pregnancy and nursing

  Hormonal shifts plus the nutritional demands of gestation and lactation can cause:

  • Increased shedding

  • Temporary coat thinning

  • Texture changes [5]

With good nutrition and recovery time, many dogs’ coats improve again after weaning, but the process can be slow.

Aging

Older dogs may show:

• A thinner or sparser coat

• Slower regrowth after grooming or medical procedures

• More obvious changes if they develop endocrine diseases (like hypothyroidism or Cushing’s disease) [5][11][14]

Sometimes this is normal aging; sometimes it’s an early clue that something in the hormonal system needs checking.

When shedding is just seasonal – and when it might be a health flag

Every dog sheds. The challenge is telling “normal for this dog” from “this might be a problem.” There’s no single perfect rule, but there are patterns.

Normal seasonal shedding tends to:

• Peak in spring and/or fall

• Last around 2–3 weeks for double‑coated dogs [9][11]

• Be evenly distributed over the body (no sharp edges between normal and bald areas)

• Occur in a dog who otherwise:

  • Has normal energy and appetite

  • Has healthy skin (no sores, heavy dandruff, or redness)

  • Feels like their usual self

Shedding that deserves a vet conversation

It’s reasonable to bring shedding up with your vet if you notice:

• Patchy hair loss or bald spots (alopecia) [5][11][14]

• Symmetry – for example, both flanks thinning in a mirror‑image pattern (often seen in hormonal issues)

• Very slow regrowth after clipping or shaving

• Dry, brittle coat that breaks easily [5][11][14]

• Skin changes: redness, darkening, thickening, scaling, or recurrent infections

• Behavior or health changes alongside coat changes, such as:

  • Lethargy, weight gain, or feeling cold (possible hypothyroidism) [5][11][14]

  • Increased thirst, urination, or panting (possible Cushing’s disease) [5][11][14]

  • Digestive upsets, itching, or discomfort

Your vet may suggest bloodwork (including a thyroid panel or tests for Cushing’s), skin scrapings, or other diagnostics when the pattern doesn’t fit “simple seasonal shedding.”

You’re not overreacting by asking. One of the most practical uses of understanding “normal” shedding is knowing when to say, “This isn’t normal for my dog anymore.”

The role of stress: when emotions show up in the coat

Stress in dogs isn’t always dramatic. It can be:

• Chronic low‑grade anxiety

• Environmental stress (noise, crowding, frequent change)

• Physical stress from illness or pain

Research using hair cortisol concentration (HCC) shows that dogs’ stress hormones vary by season, with higher levels in winter, especially in females [12]. That suggests a subtle interplay between:

• Seasonal changes (light, routine, outdoor time)

• Hormonal stress responses

• Hair growth and shedding patterns

In daily life, you might notice:

• Extra shedding during major changes (moving house, new baby, loss of a companion)

• More coat issues when a dog is ill or in chronic pain

Stress alone isn’t usually the sole cause of heavy shedding, but it can tip the balance in a dog already dealing with other factors (hormonal shifts, nutritional gaps, skin issues).

Nutrition, environment, and grooming: how much do they really matter?

You can’t stop a biologically programmed seasonal shed – and you shouldn’t. It’s part of how the coat stays healthy. But you can influence how well the coat copes and how dramatic the fallout feels in your home.

Nutrition: fueling the hair factory

Hair is a protein‑rich, metabolically active tissue. When nutrition is sub‑optimal, the coat often shows it first.

Evidence and expert guidance suggest:

• Balanced, complete diet

  A diet that meets essential requirements for protein, fats, vitamins, and minerals supports normal hair growth and skin barrier function [8][13].

  
  

• Omega‑3 fatty acids

  Diets rich in omega‑3s (e.g., from fish oils) can promote:

  • Healthier skin

  • Shinier coats

  • Potential reduction in excessive shedding, especially when inflammation or skin dryness is part of the picture [8][13].

    
    

• Micronutrients

  Zinc, vitamin E, some B‑vitamins, and others contribute to skin and hair health. Deficiencies can exacerbate shedding [8][13].

  
  

Important: More is not always better. Overuse of supplements marketed for “shiny coats” can unbalance a diet or interact with medications. Any supplement plan is best discussed with a vet, especially if your dog has chronic conditions.

Environment: indoor comfort vs natural cycles

Modern dogs live in climate‑controlled homes with artificial light. That’s wonderful for comfort, but it can blur natural cycles:

• Artificial light may confuse the brain’s reading of photoperiod, leading to:

  • Less distinct seasonal peaks

  • More even, year‑round shedding [4]

    
    

• Stable indoor temperatures may reduce the need for a very dense winter undercoat, subtly changing coat density and timing [4].

There’s no clear evidence that indoor living is harmful to coat health; what’s still uncertain is exactly how long‑term indoor environments reshape hormonal rhythms [4]. It’s an open research question rather than a known problem.

Grooming: partnering with biology instead of fighting it

Regular grooming doesn’t change hormones, but it does:

• Help remove loose hair during exogen (shedding phase)

• Distribute natural oils along the hair shaft

• Allow you to spot early skin or coat changes

In practice:

• Double‑coated dogs often benefit from:

  • More frequent brushing during shedding seasons

  • Tools that reach the undercoat without damaging the skin

• Single‑coated or continuously growing coats (like Poodles) may need:

  • Regular trims plus brushing to prevent mats

  • Gentle handling around any thin or sensitive areas

Grooming is also a quiet way to check in: Is the coat changing? Does the skin look different? Are there new bald patches? You’re not just managing fur; you’re monitoring health.

Emotional reality: when fur on the floor feels like failure

Shedding isn’t just a biological event. It’s also:

• Hair on every soft surface

• Vacuuming more than you’d like

• Worrying that “too much fur” means “something’s wrong”

• Feeling judged (by others or yourself) for not staying ahead of it

For many owners, especially those caring for dogs with chronic shedding or endocrine issues, this can become a source of ongoing stress and guilt:

• “If I groomed more, would she be healthier?”

• “Is this my fault because she lives indoors?”

• “Am I missing a serious illness?”

Veterinary teams see this regularly. One of their challenges is reassuring owners when shedding is normal – without dismissing concerns, and without missing the cases where shedding really does signal disease.

A few grounding thoughts:

• Seasonal shedding in a healthy dog is not a sign of neglect. It’s a sign of a working endocrine system.

• You are allowed to find it annoying and still be a deeply caring owner.

• Being unsure where “normal” ends is exactly why vets exist. Asking doesn’t make you neurotic; it makes you observant.

If shedding is contributing to burnout – especially in the context of other caregiving duties – that emotional load is as real as the fur you’re sweeping up.

Talking with your vet: making shedding a useful clinical clue

Shedding conversations with vets often circle around the same core question: “Is this normal for this dog, at this stage of life, in this environment?” You can make that conversation more precise and less stressful by bringing specific observations.

Consider noting:

• Timing and pattern

  • When did the shedding increase?

  • Does it happen every spring/fall, or is this new?

  • Is it generalized or patchy?

    
    

• Life changes

  • Recent heat cycle, pregnancy, or nursing?

  • Neutering/spaying?

  • Major stressors (move, new pet, loss, illness)?

    
    

• Other symptoms

  • Changes in thirst, urination, appetite, weight

  • Changes in energy, behavior, or comfort

  • Skin changes (redness, odor, sores, flaking)

    
    

Vets may recommend:

• Watchful waiting with supportive care when the pattern fits normal seasonal shedding.

• Diagnostic tests (e.g., thyroid panels, endocrine testing, skin exams) when:

  • Shedding is abnormal for the dog

  • There are bald patches or skin lesions

  • Other systemic signs are present [5][11][14]

You’re not expected to sort this out alone. Your role is noticing; theirs is interpreting.

The ethics and gray areas: comfort, cleanliness, and chronic disease

A few tensions often sit quietly in the background of shedding discussions:

• Dog comfort vs human convenience: It’s natural to want less fur in the house. At the same time, some coat management choices (like shaving certain double‑coated breeds) can affect how the coat regrows and functions. Finding a balance that respects the dog’s biology and the household’s sanity can be tricky.

  
  

• Supplements and “miracle” promises: The pressure to fix shedding can make heavily marketed coat supplements tempting. Without guidance, though, there’s a risk of:

  • Unnecessary expense

  • Nutritional imbalance

  • Masking an underlying medical issue

    
    

• Chronic endocrine diseases and quality of life: When shedding is a symptom of long‑term conditions like hypothyroidism or Cushing’s disease, treatment can be lengthy and sometimes imperfect. Owners and vets may face hard questions about:

  • How aggressively to treat

  • How to weigh appearance vs comfort vs side effects

  • When ongoing treatment is helping – and when it may no longer be in the dog’s best interest

There are no one‑size‑fits‑all answers. But naming these tensions can make decisions feel less lonely and more intentional.

What we know for sure – and what science is still figuring out

It can be calming to know where the science is solid and where it’s still evolving.

Well‑established [2][3][4][5][9][10][11][14]:

• Dogs, especially double‑coated breeds, have seasonal shedding peaks in spring and fall, largely driven by photoperiod‑related hormonal changes.

• Double‑coated breeds shed more and more seasonally than single‑coated breeds.

• Hormonal imbalances (thyroid, sex hormones, cortisol) can cause abnormal shedding or alopecia, often with other systemic signs.

• Owner stress around shedding and coat care is common and can affect how care plans are followed.

Still uncertain / emerging [3][4][7][12][13]:

• The precise molecular pathways linking specific hormones to each hair cycle phase in dogs are not fully mapped.

• The long‑term impact of indoor living (artificial light, climate control) on hormonal cycles and shedding regulation remains under study.

• The complex genetic interactions that determine shedding patterns – and how far we should go in breeding for “low‑shedding” traits – are active areas of research.

• The psychological impact on dogs of disrupted shedding cycles or chronic illness is not well understood, though stress clearly interacts with coat health.

Science will keep refining the details. But for daily life with your dog, the current map is already rich enough to use.

Living with the seasons in your dog’s coat

Your dog’s shedding is not random. It’s a visible, tangible expression of an internal rhythm: light and dark, hormones rising and falling, cells growing and resting.

You don’t have to love the fur tumbleweeds. You don’t have to pretend the extra cleaning is fun.

But you can reframe what you’re seeing:

• Seasonal shedding in a healthy dog is a sign of a system that responds to the world.

• Changes in shedding over time are information, not instant verdicts – clues you can bring to your vet, not evidence that you’ve done something wrong.

• The goal is not to stop shedding, but to understand it well enough that you can tell when it’s simply spring… and when it might be hormones asking for help.

Somewhere between the vacuum and the vet visit, there’s a quieter space: noticing, asking, adjusting. That’s where most of dog caregiving lives – and where your attention to a “simple” thing like fur on the floor can quietly protect your dog’s long‑term health.

References

1. Joii Pet Care. Shedding and hormones study example.

2. American Kennel Club (AKC). Seasonal shedding and management.

3. Pacagen, citing National Institutes of Health (NIH) studies on hormonal effects and photoperiod in dogs.

4. Animal Friends Dermatology. Coat types and shedding timing in dogs.

5. PetCareRx. Hormonal imbalances and shedding causes in dogs.

6. NutriSource Pet Foods. Shedding as a natural function and the role of nutrition.

7. Wisconsin Designer Doodles. Genetics of shedding in dogs, including the MC5R gene.

8. Primped Pooches. Nutrition and grooming for shedding control in dogs.

9. Sun Vet Animal Wellness. Causes and management approaches for shedding in dogs.

10. ASPCA Pet Health Insurance. Understanding coat types and shedding patterns in dogs.

11. Roundwood Vets. Managing seasonal shedding and its health links in dogs.

12. Roth LS, Faresjö Å, Theodorsson E, Jensen P. Hair cortisol varies with season and lifestyle and relates to human interactions in German Shepherd dogs. Scientific Reports.

13. Seaweed for Dogs. Nutritional and stress‑related approaches to reducing excessive shedding.

14. Paradis M. Canine noninflammatory alopecia: classification and hormonal role. Veterinary Dermatology. Sage Journals.