Imma Be Queen of Leptin

Many of us are waking up to the rather unwelcome slow-down of our metabolism now that we've hit 35 or 45 or 55 years. What helps? Becoming a master of the forces that shape your metabolism and how they interact with your other hormonal systems. Leptin is a major driver, and a lesser-know hormonal cousin to insulin, so I thought I'd repost my guest blog from Dear Thyroid on the leptin scoop - how it controls metabolism, how it relates to your sluggish thyroid and the muffin around your middle.

Ever wonder why you still feel hypothyroid yet your TSH is normal? Or why the weight you gained while hypothyroid hasn’t fallen away? A key intermediary hormone that many of us are unacquainted with is leptin, a regulator of both body weight and your thyroid control. Let leptin become your new BFF by getting to know her intimately and learning how she rocks your thyroid and weight.

If you haven’t heard of leptin, that’s because it was discovered relatively recently in 1994. It’s similar to insulin in its job description. Leptin acts as an important control system that makes telephone calls to other organs about the state of your fat balance and whether to go or stay in low-metabolism survival mode. It’s made in your fat cells, and more fat cells = higher leptin levels. The high leptin normally tells your hypothalamus that you don’t need to eat as much, so metabolism slows (you make more TRH, and this raises TSH) and the TSH tells your thyroid to crank out more thyroid hormone. This is when your leptin is communicating clearly and functionally, and your hypothalamus is responding appropriately.

Optimal Leptin

Ideally, leptin should be between 4-6. If your leptin is 4-6, your hypothalamus is getting the correct phone calls from leptin. If your level is above 10, your leptin receptors are fatigued, and the phone calls are no longer getting to or from the hypothalamus. Result? Metabolism slows inappropriately because the hypothalamus is interpreting the messages inappropriately.

Problem with Chronic Dieting

Chronic dieting and/or major stress are a common cause leptin resistance. As a result, leptin no longer has a clear line of communication with your hypothalamus and thereby your metabolism. Leptin resistance makes the hypothalamus believe that you are in starvation mode, and you make more fat, and slow down thyroid hormone production. TSH goes down, you don’t convert as much T3 (active thyroid hormone) from T4 (inactive), reverse T3 goes up, appetite increases (crazy unfair, sorry about that), and often you become insulin resistant, and slow down lipolysis (fat breakdown). More fat accumulates, you’re hungrier and you age prematurely. Not good!

Over time, you get fatter, especially at the mid-section, and it becomes increasingly difficult to lose the weight and fat. In fact, it takes herculean efforts.

High Leptin Renders TSH Unreliable

As if herculean efforts weren’t enough, If your leptin is high, TSH less reliably reflects your tissue level of thyroid hormones. For example, in diabetics who are almost universally leptin-resistant, T4-to-T3 conversion is cut in half without a change in TSH. While you may not be diabetic, you may still experience a significant reduction in your conversion before your TSH picks it up. This is where, yet again, measuring your free T3 (fT3) and reverse T3 (rT3) can help elucidate the issues.

More Bad News: Leptin & Thyroid Cancer

When your leptin rises in the blood, it increases (upregulates) leptin receptors on thyroid cancer cells causing them to become more aggressive. Does it help transform normal thyroid cells into malignant cells? We don’t know. But we do know that overzealous leptin receptors were found in 80% of thyroid cancers in one series published in 2009. Leptin has been shown to stimulate growth of thyroid cancers and reduce cell death.

How About PCOS?

Short version: leptin problems cause PCOS, both in lean and obese women. The science is quite complex, and involves loss of the timing of certain hormonal rhythms of both growth hormone and luteinizing hormone. From your comments to the last post, I’d like to offer a future blog post on all things PCOS, so please comment your questions and concerns.

OK, OK… Tell Me What to Do

Measure your leptin level. If it’s above 10, use nutrition as a first strategy to reset your level. I find that 70-80% of my patients are successful just by making the nutritonal changes that are recommended for reversing leptin resistance, such as Dr. Ron Rosedale’s program (http://www.drrosedale.com) or Byron Richards 5-step plan. Dr. Rosedale presents a food program in his book that includes elimination of fruit except avocadoes and olives for three weeks and limited starchy foods. There is far more detail in his book. I find the food changes are the primary way to lower leptin; nutraceutical supplements are another approach that may augment your success with leptin-sensitizing foods.

Here again (similar to what we reviewed in my blog post last week), we want to normalize both the thyroid and the leptin levels simultaneously for the best results. What works in those who are not successful with the nutritional program to lower leptin is to add prescription therapies. I don’t like the prescription approach – I favor using natural therapies but they require deep commitment to change old eating patterns. HCG treatment has also been successful, but that’s a hugely controversial approach that merits it’s own blog post!

While leptin resistant, make sure your free T3 and reverse T3 are being managed properly. I like to see the free T3 mid-range for your lab, and the fT3/rT3 >1.8 (when fT3 is in units of ng/dl).

As leptin lowers, your TSH will more accurately reflect your tissue levels, assuming you are also limiting stress and exposure to endocrine disruptors such as bis-phenol A (BPA) and other lovelies that mess with your thyroid receptors. One side note: probiotics have been shown to reduce BPA absorption, but that’s a big topic for another post too!

If I’m making this sound as if we have the whole leptin scene figured out, let me also mention that there’s a lot we don’t know. How insulin resistance interacts with, or causes leptin resistance, for instance, is still not completely clear.

Personally, I’ve found that optimizing leptin makes my thyroid care and weight management much more successful. I’ve reversed my leptin from 11 to 4 in 6 months. As the Black Eyed Peas might put it: “Imma be Queen of my leptin, getting it down lower than 6, Imma be the flyest chick….”