Will my FSH level decrease after addressing iatrogenic hyperthyroidism, weight loss, and stress?

FSH Levels in Iatrogenic Hyperthyroidism

Your FSH level of 10.5 IU/L is likely elevated due to your iatrogenic hyperthyroidism (TSH 0.01), and it should normalize once your thyroid function is corrected, though the evidence for this specific scenario is limited.

Understanding Your Current Situation

Your hormone profile reveals several interconnected issues:

• Iatrogenic hyperthyroidism with severely suppressed TSH (0.01) is a known cause of secondary hormonal disturbances 1
• FSH 10.5 IU/L is mildly elevated for a male (normal range typically 1.5-12.4 IU/L)
• LH 7.7 IU/L is within normal range
• SHBG 95 nmol/L is elevated (normal male range 18-54 nmol/L)
• Testosterone 40 nmol/L (approximately 1154 ng/dL) is actually high-normal to elevated

Why Your FSH May Be Elevated

Hyperthyroidism directly affects the hypothalamic-pituitary-gonadal axis. The elevated SHBG is characteristic of hyperthyroidism and binds more testosterone, potentially creating a relative free testosterone deficiency that could stimulate FSH production 1. Additionally:

• Stress and weight loss independently suppress gonadotropin secretion, creating conflicting signals 1
• Iatrogenic hyperthyroidism causes metabolic stress that disrupts normal hormonal feedback loops 1
• The combination of high SHBG with normal-high total testosterone suggests your free (bioavailable) testosterone may be lower than it appears

Expected Changes After Thyroid Correction

Your FSH should decrease once euthyroidism is restored, based on the following:

• Correcting hyperthyroidism normalizes SHBG levels, which typically fall by 30-50% within 3-6 months 1
• As SHBG decreases, free testosterone increases, reducing the stimulus for FSH production
• The metabolic stress from hyperthyroidism resolves, allowing normal hypothalamic-pituitary function to resume 1

Recommended Monitoring Strategy

Recheck your complete hormone panel 8-12 weeks after achieving stable euthyroid status (TSH 0.4-4.5 mIU/L):

• Measure TSH, free T4, FSH, LH, total testosterone, and SHBG simultaneously 1
• Calculate free testosterone using total testosterone and SHBG
• If FSH remains elevated after thyroid normalization, consider testicular ultrasound and further evaluation 1

Important Caveats

Do not interpret isolated FSH elevation as testicular failure while hyperthyroid. The constellation of findings—suppressed TSH, elevated SHBG, weight loss, and stress—creates a complex hormonal milieu that makes accurate assessment impossible 1. Your relatively preserved testosterone and LH suggest primary testicular function is likely intact.

Address weight restoration concurrently. Weight loss itself suppresses gonadotropin secretion, and weight regain after hyperthyroidism treatment is expected and physiologic 2, 3, 4. Aim for gradual weight restoration to your baseline as thyroid function normalizes.

Timeline for Reassessment

• Immediate priority: Correct iatrogenic hyperthyroidism by adjusting thyroid medication dosing 1
• 6-8 weeks: Recheck TSH and free T4 to confirm euthyroid status
• 8-12 weeks after stable euthyroidism: Repeat full hormone panel including FSH, LH, testosterone, SHBG 1
• If FSH remains >10 IU/L after 3 months of euthyroidism: Consider referral to endocrinology for further evaluation 1

The key is patience—allow adequate time for hormonal axes to recalibrate after correcting the underlying thyroid dysfunction before drawing conclusions about gonadal function.