Does Poor Nutrition Raise FSH?
No, poor nutrition typically does not raise FSH levels; instead, it disrupts the hypothalamic-pituitary-gonadal axis leading to decreased LH pulsatility while FSH secretory patterns remain relatively preserved, ultimately causing menstrual dysfunction through reduced estradiol and progesterone rather than elevated gonadotropins. 1
Mechanism of Nutritional Impact on Reproductive Hormones
Poor nutrition—specifically low energy availability—primarily affects the hypothalamic GnRH pulse generator, which selectively reduces pulsatile LH secretion without adversely affecting FSH secretory patterns 2. This creates a distinctive hormonal profile:
- LH is preferentially suppressed through disrupted GnRH pulsatility when energy availability falls below critical thresholds 1
- FSH levels remain relatively stable or may even show minimal changes during nutritional deficiency 1, 2
- The downstream consequence is decreased estradiol and progesterone, not elevated gonadotropins 1, 3
Hormonal Changes in Low Energy States
When energy availability drops below 30 kcal/kg fat-free mass per day, the following hormonal alterations occur 1, 4:
- Decreased estradiol
- Decreased progesterone
- Decreased leptin
- Increased ghrelin and cortisol
- Decreased insulin and IGF-1
- Decreased thyroid hormones (T3, T4)
- Disrupted LH pulsatility with relatively preserved FSH
Clinical Context: When FSH Actually Rises
It is critical to distinguish nutritional deficiency from other causes of amenorrhea where FSH does increase 3:
- Primary ovarian insufficiency (POI): Characterized by elevated FSH and LH due to ovarian failure 3
- Menopause: Natural cessation of ovarian function with high FSH 4
- Ovarian damage: From chemotherapy, radiation, or surgery causing elevated FSH 4
In contrast, functional hypothalamic amenorrhea (FHA) from poor nutrition shows low-to-normal FSH with suppressed LH 1, 3.
Measurement Challenges
A critical caveat: Proper characterization of FSH levels requires overnight blood sampling at minimum 3 times per hour (preferably 6 times per hour) due to pulsatile release patterns 1. Single random FSH measurements may not accurately reflect the true hormonal status in nutritionally deficient individuals.
Special Population: Male Reproductive Effects
In males with obesity and poor nutrition, a different pattern emerges with decreased testosterone, LH, and FSH levels alongside elevated estrogen from increased aromatization 5. This represents hypothalamic-pituitary-gonadal axis dysfunction rather than FSH elevation.
Clinical Implications
The absence of FSH elevation in nutritional deficiency is diagnostically important: If a patient with amenorrhea and suspected poor nutrition presents with elevated FSH, consider alternative diagnoses such as primary ovarian insufficiency rather than functional hypothalamic amenorrhea 3. The hormonal signature of nutritional deficiency is suppressed LH with low estradiol, not elevated gonadotropins.