Hyperpigmentation

What it is

Hyperpigmentation is one of the most common skin conditions seen in clinical practice, affecting an estimated 90% of pregnant women in its hormonal form (melasma) and occurring across all skin types and ethnicities. Also called hypermelanosis, hyperpigmentation is an umbrella term for any condition in which localized or generalized areas of skin appear darker than the surrounding tissue due to excess melanin production. While not medically dangerous on its own, it can signal an underlying hormonal disorder — most notably adrenal insufficiency — and causes significant psychosocial distress in many patients. In Canada, people with darker skin tones (Fitzpatrick types IV–VI), who make up a growing proportion of the population, are disproportionately affected because higher baseline melanin content makes pigmentation changes more visible and harder to treat.

There are four clinically distinct subtypes:

Subtype	Primary trigger	Typical location
Melasma	Hormones (estrogen/progesterone), UV	Cheeks, forehead, upper lip, chin
Post-inflammatory hyperpigmentation (PIH)	Skin inflammation or injury	Site of prior acne, eczema, burns
Solar lentigines (age/liver spots)	Cumulative UV exposure	Face, hands, forearms
Addison's disease pigmentation	Elevated ACTH	Skin folds, scars, gums, knuckles

Causes and mechanism

Melanin is produced by melanocytes in the basal layer of the epidermis. Any stimulus that activates these cells — hormonal, inflammatory, or phototoxic — can cause localized or diffuse overproduction.

Hormonal pathways are the most relevant in a hormone-health context:

• Estrogen and progesterone directly stimulate melanocytes to upregulate melanin synthesis. This is the primary driver of melasma in pregnancy and in people using combined hormonal contraceptives. Progesterone-only methods appear to carry lower risk, though evidence is still accumulating.
• Elevated ACTH in Addison's disease (primary adrenal insufficiency) causes generalized darkening because ACTH shares a receptor with melanocyte-stimulating hormone (MSH). The pituitary overproduces ACTH in an attempt to drive damaged adrenal glands, inadvertently activating melanocytes throughout the body — particularly in pressure areas, skin folds, and existing scars.
• Thyroid dysfunction — both hypothyroidism and hyperthyroidism — can alter pigmentation patterns through secondary effects on skin cell turnover and vascular tone, though the mechanism is less well characterized than the estrogen or ACTH pathways.

Non-hormonal causes include UV radiation (the most common trigger for solar lentigines and a major exacerbating factor for melasma), post-inflammatory responses from acne, eczema, or psoriasis, and certain medications — tetracycline antibiotics, antimalarials, and some chemotherapy agents among them. Genetic predisposition also plays a role, particularly in melasma.

Symptoms and diagnosis

Hyperpigmentation presents as areas of skin darker than the surrounding tissue. The pattern and distribution guide the likely cause:

• Melasma appears as symmetrical brown or grey-brown patches on the cheeks, forehead, upper lip, and chin. It affects women in approximately 90% of cases and worsens with sun exposure.
• PIH produces dark marks at the exact sites of prior inflammation — acne lesions, eczema plaques, cuts, or burns. Depth of inflammation determines whether pigment is epidermal (more responsive to treatment) or dermal (slower to resolve).
• Addison's disease pigmentation is generalized, affecting sun-exposed skin, pressure points, oral mucosa, and scars. This pattern — especially when accompanied by fatigue, weight loss, or salt craving — warrants urgent investigation for adrenal insufficiency.

Diagnostic workup typically involves:

1. Clinical examination of pattern and distribution
2. Wood's lamp (UV light) to determine pigment depth — epidermal pigment fluoresces; dermal pigment does not
3. Hormone panel (estrogen, progesterone, TSH, cortisol, ACTH) when a hormonal cause is suspected
4. Skin biopsy in diagnostically uncertain cases

In Canada, hormone panels are available through LifeLabs and Dynacare; requisitions can be initiated by a family physician, dermatologist, or endocrinologist.

Treatment options

Treatment is guided by subtype and underlying cause. Sun protection is the single most important intervention for any form of hyperpigmentation — daily broad-spectrum SPF 30 or higher is the foundation of every treatment plan, because UV exposure will undermine even prescription-strength topical therapy.

For melasma and hormonal hyperpigmentation:

• Topical hydroquinone (2–4%, by prescription in Canada) inhibits the enzyme tyrosinase, reducing melanin synthesis. It is the most evidence-backed first-line agent but should not be used continuously for more than 3–6 months.
• Tretinoin (topical retinoid) accelerates epidermal cell turnover, clearing pigmented cells faster. Often combined with hydroquinone.
• Azelaic acid (15–20%) reduces melanin production and has anti-inflammatory properties; it is considered safe in pregnancy when other agents are not.
• Kligman's formula — a compounded combination of hydroquinone, tretinoin, and a mild corticosteroid — is used for resistant melasma under dermatologist supervision.
• Addressing the hormonal trigger: if combined oral contraceptives are the precipitant, switching to a progestogen-only or non-hormonal method may reduce recurrence.

For PIH: the same topical agents apply, alongside treatment of the underlying inflammatory condition (e.g., acne management).

For Addison's disease pigmentation: effective cortisol and aldosterone replacement lowers ACTH levels; skin darkening typically fades gradually over several months as ACTH normalizes.

For resistant cases: chemical peels, fractional laser, Q-switched Nd:YAG laser, and intense pulsed light (IPL) are options available through dermatology clinics across Canada. These carry higher risk of PIH in darker skin tones and require an experienced provider.

When to see a clinician in Canada

Seek assessment from a family physician or dermatologist if:

• New or rapidly spreading skin darkening appears, particularly on the face
• Darkening follows an unusual pattern — generalized involvement of skin folds, scars, oral mucosa, or pressure points — as this can indicate adrenal insufficiency requiring urgent investigation
• Over-the-counter treatments have not produced improvement after 3–6 months
• You are pregnant and have developed significant facial pigmentation
• You are using hormonal contraceptives and have developed new facial pigmentation

Canadians in provinces with telehealth coverage can access initial dermatology or hormone assessments through platforms such as Maple, Felix, Cleo, or Phoenix, though in-person Wood's lamp examination and skin biopsy require a physical visit. Prescription topical agents (hydroquinone, tretinoin) require a clinician's prescription under Health Canada regulations and are not available over the counter at therapeutic concentrations.

Limitations and open questions

Research is still emerging on several aspects of hyperpigmentation management. The long-term safety of hydroquinone beyond 6 months of continuous use is not fully established, and Health Canada has not issued updated guidance specifically on compounded Kligman's formula. The relative contribution of visible light (as distinct from UV) to melasma worsening is an active area of investigation — some evidence suggests tinted, iron-oxide-containing sunscreens may outperform standard UV-only formulas for melasma, but head-to-head Canadian trial data are lacking. The role of oral tranexamic acid — increasingly used off-label for melasma — has promising short-term evidence but limited long-term safety data, and it is not yet endorsed in Canadian dermatology guidelines. For people with darker skin tones (Fitzpatrick IV–VI), laser and light-based treatments carry a meaningful risk of worsening PIH, and optimal protocols for this population remain under study.