Persistent symptoms after COVID-19 are increasingly recognised as more than prolonged tiredness. 

In a proportion of individuals, long COVID reflects measurable biological changes, particularly involving hormones that regulate stress, energy, and recovery. 

Research suggests that some people with long COVID show lower cortisol levels and subtle disruption of key endocrine pathways, including the hypothalamic–pituitary–adrenal (HPA) axis and, in selected cases, growth hormone signalling. 

Other hormone systems appear far less consistently affected at a population level.

Post-Viral Fatigue & Hormones

Post-viral fatigue in long COVID is not simply due to deconditioning. 

In some individuals, it reflects altered stress-hormone signalling. 

Studies show that a subset of people with long COVID have lower-than-expected cortisol levels, which may contribute to….

• Fatigue
• Brain fog
• Dizziness
• Reduced tolerance to standing. 
  
  

Reduced responsiveness of pituitary signalling may also slow recovery. 

While this does not imply that everyone has an endocrine disorder, it supports targeted hormonal assessment when symptoms persist.

Menstrual Irregularities & Reproductive Hormones

Menstrual changes following COVID infection or vaccination have been reported, but they are usually mild and temporary. 

Short-term immune activation and stress can briefly influence reproductive hormone signalling, leading to small shifts in cycle timing. 

Importantly, these changes do not suggest permanent hormonal damage and typically resolve within one or two cycles.

Thyroid Dysfunction

True thyroid injury after COVID-19 is uncommon. 

Although early reports of subacute thyroiditis raised concern, large population studies have not shown a sustained increase in thyroid disease linked to either infection or vaccination. 

A2024 population-based study found no association between SAT and either COVID infection or vaccination at 30,60, or 90 days before diagnosis. Cortisol and Stress Hormones

Cortisol plays a central role in energy regulation, blood pressure control, and immune balance. 

In a subset of individuals with long COVID, cortisol levels appear lower than expected. 

This may contribute to symptoms such as……

• Fatigue
• Nausea
• Dizziness
• Low blood pressure. 
  
  

Current evidence suggests this reflects a temporary disruption of the HPA axis rather than permanent adrenal damage in most cases.  

Insulin & Metabolic Hormones

COVID-19 can affect glucose regulation in some individuals after infection. 

Evidence indicates a higher short-term risk of insulin resistance and new-onset type 2 diabetes in certain populations. 

This appears to reflect post-infection metabolic disruption rather than inevitable long-term disease, highlighting the importance of monitoring glucose control, particularly in those with existing metabolic risk factors.

Growth Hormone & Recovery

Growth hormone supports tissue repair, metabolic balance, and recovery. 

In some people with long COVID, growth hormone secretion appears reduced, suggesting impaired recovery signalling rather than permanent deficiency. 

Specialist assessment is required before any diagnosis is made. 

Overlap of Symptoms

Many long COVID symptoms overlap across systems, including…

• Fatigue
• Palpitations
• Brain fog
• Poor sleep.
  
  

These may arise from a combination of….

• Autonomic dysfunction
• Hormonal disruption
• Sleep disturbance
• Anaemia, 
• Altered glucose regulation.  
  
  

Because symptoms are non-specific, a structured, symptom-led assessment is essential to guide appropriate investigation and avoid unnecessary treatment.

Are there Hormonal Disturbances post-COVID Vaccination?

Hormonal effects following COVID-19 vaccination are generally mild and short-lived. 

Temporary menstrual cycle changes have been reported, but cycles usually return to baseline within one or two months. 

Current evidence does not support a link between vaccination and long-term hormonal disorders, including thyroid disease.  

Diagnosis & Monitoring

Hormonal testing after COVID-19 should be guided by symptoms rather than routine screening. 

Persistent fatigue, dizziness, or low blood pressure may justify a morning cortisol test, with further evaluation if results are borderline. 

Symptoms such as palpitations or heat intolerance warrant basic thyroid blood tests, while individuals with weight gain or metabolic risk may benefit from periodic glucose monitoring. 

Advanced hormone testing is reserved for clear clinical indications.

Management & Recovery

Management depends on the hormonal system involved. 

Thyroiditis is usually self-limiting and managed symptomatically. 

Confirmed central adrenal insufficiency may require short-term physiological hydrocortisone replacement, with planned reassessment as recovery often occurs. 

Disturbed glucose control is managed with lifestyle support and standard diabetes care where needed. 

Growth hormone replacement is considered only in confirmed deficiency under specialist supervision. 

Targeted, diagnosis-led care is preferred over routine steroid use or non-specific supplements.

Summary

Hormonal changes after COVID-19 are variable and do not represent a single condition. 

Evidence points to lower cortisol and reversible HPA-axis disruption in a subset of individuals, alongside a modest increase in post-COVID metabolic risk. 

Thyroid involvement appears uncommon and largely reflects background population patterns. 

The key clinical message is to investigate when symptoms suggest specific endocrine involvement, treat confirmed abnormalities, and recognise that many hormonal disturbances improve over time.


Hema, is a Specialist Dietitian at The London Obesity & Endocrine Clinic. She has helped many patients overcome weight management barriers. ©Simplyweight

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