Why is My Period Late: 6 Possible Reasons Why Your Period is Missing

Having a late period can be very distressing, especially if you are used to having regular periods or are concerned about an unexpected pregnancy.

Firstly, if pregnancy is a possibility then have that assessed. If you have checked that box, then what next?

There are many variables that influence the menstrual cycle and can disrupt the timing of when your period shows up.

Here are 6 reasons why your period could be late:

  • STRESS – also called Functional Hypothalamic Amenorrhea (FHA)
    • FHA is one of the most common causes of missing periods.
    • The stress can be from emotional stress or physical stress such as not eating enough, over-exercising or chronic illness. Our bodies perceive emotional stress and physical stress the exact same way.
    • When our bodies feel stressed, they release CRH, ACTH, and cortisol which inhibit gonadotropin-releasing hormone (GnRH). GnRH is a hormone released from the brain and is responsible for initiating the cascade of messengers that lead to egg production and reproductive function.
    • This makes sense from an evolutionary standpoint. If the body is in distress, it’s understandable that it would prevent reproduction as it would not be practical to make and rear a child while in a famine or running away from predators. Many species have the ability to put their pregnancy on pause in response to stress. Humans are not that capable, so we need to ensure that conditions are favorable for child manufacturing prior to allowing conception.
    • PCOS is associated with elevated androgen levels (testosterone) and insulin resistance. This combination messes with normally occurring hormone levels and also makes the ovary less responsive to hormone signalling. This leads to the egg not being released and cysts to form on the ovaries as a result of this hormone imbalance.
    • When our thyroid doesn’t secrete enough hormones (T4 and T3), then the hypothalamus in the brain will secrete high levels of TRH which will increase TSH release from the pituitary gland which in turn will stimulate the thyroid to produce more hormones. TRH also stimulates prolactin secretion. Prolactin is a well-known inhibitor of GnRH. It’s responsible for halting menstruation during pregnancy and breast-feeding.
    • When nearing the onset of menopause cycles become more irregular and can get longer and longer.
    • As the body senses the scarce amount of viable follicles (eggs), this leads to a tumultuous hormonal environment. This can cause longer cycles up until the menstrual cycle ceases completely.
    • GnRH suppressors – opioids (heavy duty pain killers) and glucocorticoids (immune suppressants)
    • High prolactin levels – psychotropic meds, gastrointestinal motility meds, and Parkinson’s meds
    • Trauma to the head can result in a sluggish pituitary gland even up to a year after. A sluggish pituitary gland means sluggish signalling to your ovaries regarding ovulation.
    • If you have ever had a head injury and it lines up with when your menstrual irregularity began then it could be related.


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4333037/

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